Giorgio de Chirico, 90, one of Italy's major painters and sculptors who exerted a significant influence on the development of modern art, died in a Rome hospital Monday following a heart attack.

De Chirico, who had been ill with what were described as heart and lung ailment, was a founder of the metaphysical and surrealist schools of art. His earlier and are represented in major collections and museums around the world.

His stark "city square" landscapes of Italian pizzas and his sometimes faceless "mannequins" have been hailed as precursors of surrealism - that school of modern art in which exaggerated images are drawn from myths, nightmares and other images drawn from the subconscious.

With Carlo Carra, one of the original Italian futurists, de Chirico founded the "metaphysical school," a step toward surrealism that, in de Chirico's hands, strongly relied on architectural forms. Architecture was, in fact, one of the important facets of much of his earlier work and he described it with the same romanticism that infused many of his paintings.

"I remember one vivid winter's day at Versailles," he wrote in 1913. "Silence and calm reigned supreme. Everything gazed at me with mysterious, questioning eyes. And then I realized that every corner of the palace, every column, every window, possessed a spirit, an impenetrable soul . . . I grew aware of the mystery which urges men to create strange forms, and the creation appeared more extraordinary than the creators."

About 1917, de Chirico's work began to undergo a profound change. He turned away from virtually all forms of modern art. Instead, he embraced a type of romantic neoclassicism that was imitative of the old masters. These pictures met with substantially less critically success than his earlier work.

In an autobiography, he attributed the change - one of the major paradoxes in a life that was filled with paradoxes - to an experience he had while visiting a gallery in Rome in 1919.

"It was in the museum of the Villa Borghese one morning, standing before a Titian, that I received the revelation of what great painting was: in the gallery I beheld tongues of flame; outside, through the vastness of the bright sky, a solemn clangor echoed over the city and trumpets blared announcing a resurrection. . . ."

And so de Chirco took to copying old masters as a way of improving his own painting. He became a critic and denounced modernism and surealism - the kind of pictures on which his own reputation as an artist primarily rests. He once denounced his own work.

But in an interview with the New York Times in 1972, he rejected criticism, calling it "hare-brained." And of his own paintings, he said that all of them, "the good and the bad, the early and the late, they're all my children. Do critics mean I have produced only cadavers for 40 years?"

Apart from controversy about the value some of his paintings as art, de Chirico paintings often were the subject of controversy about their authenticity. His word frequently was copied. He once estimated that at least 3,000 pictures attributed to him - some of them shown in famous collections and hung next to his genuine work - were counterfeit.

In 1947, he asserted that a painting attributed to him and owned by an Italian art dealer was a fraud. The art dealer disputed this and won a court judgment against the artist worth about $6,000. In 1968, there was another suit over the rights to reproduce de Chirico's sculptures. De Chirico was said to have given "exclusive" reproduction rights to several different galleries at the same time.

In 1972, the New York Cultural Center held a retrospective show of de Chirico's work that included 182 pieces, many taken from his house in Rome. The show was called "de Chirico by de Chirico" and there were sculptures, drawings and lithographs, as well as paintings. It was the first show to cover his entire career.

De Chirico told the New York Times that it was the "only completely authentic de Chirico exhibition ever held. Most de Chirico exhibitions," he said, "can claim their share of fakes."

De Chirico was born of Italian parents in Volo, Greece. His father, a railroad engineer, gave him his first painting lessons and later provided private tutors for him and his brother, Andrew, a painter, poet and composer. (The brother later changed his name to Alberto Savinio).

At the age of 12, de Chirico began studying at the Ecole Polytechnique in Athens. When his father died in 1905, the family moved to Munich and de Chirico enrolled in the Munich Academy of Arts.

At the academy he came under the influence of the work of the Swiss-German painter, Arnold Bocklin, and of the German sculptor, painter and printmaker, Max Klinger. He read the German philosopher Nietzsche and Schopenhauer and became interested in psychology.

There followed a lengthy sojourn in Italy, where he lived in Florence, Turin and Milan. De Chirico continued his classical training during this period, copying old masters in museums and sketching the architecture around him.

Then he moved to Paris, the capital of the art world, and shook off the constraints of tradition, a process that already had begun while he was in Italy. His previous training came together in new forms and his "neosurrealism" began to emerge.

He became friends with Picasso and Max Ernst, the cubist. He also joined the circle of the poet Guillaume Apollinaire, whose portrait he painted in 1914.

In World War I, he returned to Italy and served in the Italian army.

By the end of the war, he was changing his ideas about art. But even as he was growing more skeptical about modernism he continued his earlier associations. He exhibited with the surrealists at their first group show at the Galerie Pierre in Paris in 1925, and contributed to the review "La Revolution Surrealiste." Others represented at the Galerie Pierre show included Picasso, Joan Miro, Paul Klee and Jean Arp.

De Chirico's autobiographical "dream novel," "Hebdomeros," published in 1929, is considered an important literary surrealist document.

As a critic de Chirico rejected most developments in the art world since his early work. He maintained that modern art was "horrible, something you can't even look at," while his own later work was based "on fact" and "reality."

In recent years, he has lived by the Spanish Steps in Rome next to the house in which the poet John Keats died in 1821.

"I stay home because from there I can see the whole world," he said." I have television, my books, photographs, and when I feel lonely I go to the movies."

He had continued to write and paint until recent years. He had done illustrations for advertisements for Fiat automobiles and for Chianti wine.

De Chirico was married to the Russian-born writer on art, Isabella Far, and with her wrote "Commedia dell'Arte Moderna" (The Comedy of Modern Art) in 1945. The couple had no children.