He is part of a family dynasty that had an unparallelled impact on our cultural and artistic heritage. He inspired a generation of artists, and today his works can fetch more than a 1m at auction. But is the phenomenon that is Jack B Yeats purely an Irish obsession or does his work . . . and the market for his paintings . . . stand international comparison?

This year is the 50th anniversary of Yeats's death and the National Gallery is hosting an exhibition entitled Masquerade and Spectacle: The Circus and the Travelling Fair in the work of Jack B Yeats. It features 22 paintings, drawn largely from private collections and rarely exhibited in public, as well as numerous sketches and drawings.

The exhibition focuses specifically on the theme of the circus . . . a lesser-known aspect of his work but one which was of great importance to the artist . . .and to which he returned again and again throughout his life. The circus pictures may seem a narrow focus but they demonstrate through a compact prism the vast stylistic and thematic changes that developed throughout a career spanning more than 60 years. This concise, carefully considered exhibition forms a microcosm through which his artistic output, and its significance, can be judged.

According to exhibition curator Roisin Kennedy, the recent tendency to focus on the monetary value of Yeats's paintings has overshadowed reflection on the work itself. "The whole market interest in Yeats has sometimes been almost negative in terms of the artist's reputation; it has tended to detract from the real contribution and meaning of his paintings. His work is incredibly complex and interesting . . . and there are just so many strands to his work. He is by Irish standards a hugely interesting and important artist in his own right, irrespective of the market for his work."

Yeats is one of the few Irish artists whose work has fetched more than a million pounds sterling . . . the record for his work is �1.2m ( 1.8m) for 'The Wild Ones' at Sotheby's in 1999 . . . which perhaps explains the intense interest in the high finance of his art. And, according to Frances Christie of Sotheby's in London, "To all collectors of Irish art, he's probably the most sought-after artist there is. The bigger, better oils are rare to the market now because they're either in public or private collections, so when they do come up there tends to be a lot of interest in them."

Whyte's managing director Ian Whyte agrees. "Of all the artists in Ireland, he would be the best investment that you could buy, probably. . . I'd say the next time you see a really good Yeats on the market you could see the record going to 5m or more."

But Bernard Williams, international director of Irish art at Christie's, sees it differently: "Internationally, the only people who buy Yeats are the people who celebrate St Patrick's Day. There are very few non-Irish-connected people who buy Yeats, so it's a small market as opposed to a Lavery or an Orpen market, who are very much international artists, and so one has to be careful and sensitive about how one markets his work. If you overprice them, they don't sell. . .A very good one is worth over a million pounds but a bad one isn't worth �100,000."

However, Theo Waddington, son of Jack B Yeats's agent Victor and a veteran art dealer, believes, "No art should be looked at just as a vehicle for money or investment.

"I wouldn't think about it in terms of the economics of taste. I would think about Jack Yeats and his family in terms of Irish art history, Irish history and international art history, " he says. "I put him alongside the great Expressionists, I put him alongside Kokoschka and Munch and I would put him next to Bonnard or Matisse. I think he's that important. I think he is, longterm, the person Ireland can look towards as our great figure in the international art world."

Masquerade and Spectacle underscores the fact that Yeats was working within an international, rather than simply an Irish, context. He is often perceived as the quintessential Irish painter and a certain mythology has built up around him and his family over the years.

"We always consider him just as a great Irish artist and so we are marginalising him to some extent, " says Roisin Kennedy.

A number of the paintings, for example, were exhibited at the Armory Show in New York in 1913, a major international exhibition of modern art which also included work by the likes of Picasso, Matisse and Duchamp.

In his lifetime, Yeats had made his mark on the international art scene, in large part due to the efforts of his agent Victor Waddington. Yeats exhibited in New York, Paris and London and even had a retrospective at the Tate in 1948. In later years, he developed a friendship with Austrian Expressionist Oskar Kokoschka, whose work had affinities with his own mature paintings. The subject of the circus, also, was one which featured frequently in the work of European modernists such as Degas, Toulouse-Lautrec and Picasso . . . although theirs was a more urban, cosmopolitan representation than Yeats's preference for local rural fairs.

Yeats, however, was also something of an individualist, who never associated himself with any particular style or movement. He set himself apart from other Irish painters of the time, being more associated with literary figures such as JM Synge and Samuel Beckett. Jack B Yeats was himself a novelist and playwright, with several plays produced at the Abbey and a number of novels published in the 1930s and 1940s.

Yeats's changing approach to the circus demonstrates how radically his artistic style developed over the years, from humorous reportage to vivid, subjective expressionism. The artist had a lifelong fascination with the circus, visiting them from his childhood up to the 1930s and 1940s and often recording what he saw in sketchbooks.

He first encountered small fairs and travelling circuses growing up in Sligo, where he had been sent to live with his grandparents . . . his father, John B Yeats, was at the time struggling to establish himself as a portrait painter in London, where Jack was born in 1871. During his years in Sligo, Yeats developed a deep love for the west; indeed, he later said, "Sligo was my school and the sky above it."

When he returned to live with his parents in London at the age of 16, he often visited circuses and Wild West shows. He spent the early years of his career working as an illustrator for periodicals while also painting watercolours. But he began to focus primarily on oil painting when he returned to live in Ireland in 1910. These early oils reveal the legacy of his training as a visual reporter, with their strong outlines and bold patterning, as well as his skill at characterisation and his interest in recording contemporary everyday life . . . particularly that of the west of Ireland.

'The Barrel Man' (1912), for example, is a curious painting which captures a rather cruel sideshow act he saw at a fair in Gort in 1903. It involved a man standing inside a barrel while members of the public threw sticks at him. Yeats's painting focuses solely on the barrel man, warding off a bombardment of sticks with a slightly crazed expression on his face.

Yeats displays a particular interest in these sideshow events, often focusing on marginalised figures within the circus, which itself existed on the fringes of society. 'The Circus Dwarf ' (1912) is a masterful example of his work from this period (interestingly, it was rejected by the RHA's annual exhibition but was included in the famous Armory Show). Surrounded by the cluttered accoutrements of circus life and with the distinctive, striped tent as a backdrop, the dwarf still cuts a striking figure, with his red jacket, clenched fist and determined expression. With Yeats he is no mere circus curiosity but a proud, dignified individual.

As Yeats's work developed in the 1920s and 1930s, he broke away from the use of strong outlines and muted, descriptive colours. Instead, he began to express emotion through colour and the application of paint.

Brushstrokes became loose and free; paint was thickly daubed on in places, squeezed straight from the tube and manipulated with a palette knife or his fingers, while the canvas was left bare in other areas. Colour was no longer purely descriptive but was used boldly and non-naturalistically to underscore emotional states. The use of memory also became increasingly important, as he once said: "No one creates. . . the artist assembles memories."

Alongside this stylistic development, his preoccupation with the circus took on a more personal, but also a more universal, meaning. 'The Last Dawn But One' (1948), painted when Yeats was in his 70s, demonstrates this. Rather than chronicling a particular event or spectacular display, this painting shows a circus troupe in the early morning, hurriedly packing up and preparing to move on. As Kennedy notes, Yeats's wife Cottie had died the previous year, after a 50-year marriage so it could be interpreted that "the endless task of setting up and taking down the circus is a metaphor for humanity's continual struggle to survive" . . .our neverending effort to keep the show on the road.

The circus also came to represent the role of art in general and Yeats identified with the tragicomic clown as an artist figure. 'Alone' (1944) shows a solitary clown standing in the centre of an empty circus ring with his head down, gazing at his hands. The scene could depict the lonely isolation of the artist but also the solitude that is necessary for creativity. While the clown is thickly painted, large areas of the background are almost completely bare: "Yeats uses the canvas of the painting literally to represent the canvas of the circus tent, " says Kennedy.

In this way, the act of painting, and the play between representation and reality, come to the fore . . . indeed, this work could be construed as a selfreflexive meditation on the creative process itself.

It is in this often overlooked context that Yeats fits into the developments in European modernism of the time. "Yeats as a pure painter has been neglected to a certain extent, " says Kennedy. "We tend to think of him as a sentimental painter, a painter of horses . . . almost what have become cliches about Yeats . . . but in fact he was a very interesting technician and a very experimental painter and he was really concerned with the artistic process and where it was going and what one could do with it. And I think that was why he was of interest to people like Samuel Beckett."

It is 50 years since Jack B Yeats died at the age of 85 and perhaps now is the time for a reassessment of his work . . . both in terms of its impact on Irish art history and its place within an international art context. Are we so inured to our idea of Yeats that we have forgotten to actually look at his paintings and to really consider what he was trying to achieve? It is often said his late paintings, at first glance, appear to be a chaotic jumble of seemingly abstract colours but that, on closer inspection, forms and shapes begin to emerge and the subject Yeats has depicted is gradually revealed. Isn't it time we also took a closer look at the legacy of Jack B Yeats?

'Masquerade and Spectacle' continues at the National Gallery of Ireland until 11 November