Katherine Ann Porter, 90, a writer who dazzled the literary world with the subtlety and power of her short stories and the author of one novel, "Ship of Fools," which added a fortune to her fame, died Thursday at the Carriage Hill Nursing home in Silver Spring. She had a series of strokes.

Miss Porter's numerous honors included the Pulitzer Prize, awarded to her in 1966 for her short stories, the National Book Award for fiction in the same year, and the Gold Medal of the National Institute of Arts and Letters the following year.

Although her reputation is anchored most firmly in her short stories and novellas, of which she published five volumes, Miss Porter maintained that there was a coherence that ran through her shorter works and "Ship of Fools." tGiven Miss Porter's reputation, it is not without irony, perhaps, that the appearance of the novel in 1963 was greeted more as a publishing than a literary event. But a publishing event it certainly was. The book went to the top of the best seller list and the film rights were sold for a reported $500,000. In fact, it met with less success with the critics than with the public.

Of this phenomenon Miss Porter said in an interview in 1970:

"People don't read very attentively. Everything I've written, from 'Flowering Judas' to 'Pale Horse, Pale Rider' through 'Ship of Fools,' is one continuous line. But I suppose it's a horrible job to ask anyone to read five books just to find out what 'Ship of Fools' is about."

And Robert Penn Warren, himself a Pulitzer Prize-winning author and poet, said in a statement shortly before Miss Porter's death: "She is certainly unsurpassed in our century or country -- perhaps any time or country -- as a writer [of] fiction in the short forms of the story or novella. Her famous and only novel . . . through to a number of critics it has seemed little more than a collection of vignettes and episodes, with no significant unity, remains a memorable work.

"I myself am inclined to feel that whatever sprawl can be found here is jerked into focus by sleight of hand, at the last moment, on the last page as it were -- with the glimpse of the poor little German youth in the ship's band. But forgetting this book, her work remains a monument to a tremendous talent -- even genius. It is permanent."

Virtually all critics wrote of Miss Porter's style, her control, the Keenness with which she perceived and recorded emotion and character. And they spoke of her toughness. In the words of Warren, her toughness was "honed to a razor edge."

In addition to "Flowering Judas," published in 1930, and the celebrated "Pale Horse, Pale Rider," the title story of which is about a love affair involving a World War I soldier who dies of influenza, which appeared in 1938, Miss Porter's other short story collections include "Hacienda: A Story of Mexico" (1934), "Noon Wine," (1937) and "the Leaning Tower and Other Stories" (1944). She also published several collections of her stories in addition to essays and other writings.

This relatively modest list by no means represents the total of her work, for Miss Porter made her living as a writer all of her life. She regarded much of what she did as hack work and it took many forms, including magazine pieces and a time in Hollywood doing film scripts. She worked for a newspaper in Denver ("A newspaper is no place to learn to write," she remarked. "The truth is newspapers simply ruin writers"), was an actress in little theaters, took photographs, played the piano and collected old music, translated French ballads, 17 of which were published as "French Songbook" in 1933, studied ballet, rode horseback, and at all times was entirely her own person ("It would be a disaster to have a man fall in love with me," she said. p"They aren't content to take what I can give; they want everything from me.").

The stories about which she cared were another matter, and she spoke of this writings as "the single vital issue" of her life.

"I could not make a living writing because I would not write the kind of books editors wanted me to write because that was mine and I wouldn't tamper with it," she said on a television program in 1962.

The "one basic idea" of her work, she said, was that of "illusion, delusion and self-deception. People never know quite what they are, and they don't know how to treat other people. As a child, it struck me how little one person could understand another. I've been told so often what I think and feel, and, of course, they've got it all wrong. I wish they'd keep out of my mind if they're going to muddle around like that."

In "Ship of Fools" these themes are presented as an allegory played out by 40 characters on a German ship, the Vera, sailing from Vera Cruz, Mexico, to Bremerhaven, Germany. Its theme is that good and evil exist in a symbiosis in which neither can exist without the other. Among the themes is the evil in German character and civilian that appears with the rise of Hilter.

Katharine Anne Maria Veronica Calista Russell Porter was born on May 15, 1890, at Indian Creek, a town near San Antonio, Tex. Her father was a farmer whose family contained some notable people. He was a direct decendant of Jonathan Boone, brother of the famous Daniel, and one of his second cousins was O. Henry (William Sidney Porter), the short story writer.

By Miss Porter's account, her family was literate, but not literary. "I was raised on a little farm in Texas, but I remember a first edition of Dr. Johnson's dictionary on the floor," she said.

Miss Porter was educated at girls' schools in Texas and Louisiana. In later life, she described herself as "precociou, nervous, rebellious, unteachable child." Like many young women of her generation, she was taught to sing and loved it.

Her interest in literature was voracious and self-generating. It also was without formal guidance, a circumstance that has been cited in efforts to explain the force and orginality of her work. She never went to college. But in the course of he long life she taught, read her work, or otherwise was formally in touch with students at more than 200 colleges and universities here and abroad. She began to write when she was a girl.

"I did not choose this vocation," Miss porter said, "and if I had had any say in the matter, I would not have chosen it."

In 1918, during the great influenza epidemic, she nearly died of the disease. In the 1920s, she lived for several years in Mexico. In the 1930s, she lived in Pais and elswhere in Europe, meeting, among others, Hitler and Goebbels, whom she described as "detestable and dangerous." These experiences and her native Texas all provided settings for her stories. tFor more than 20 years, Miss Porter lived in Washington and its environs and maintaned a residence in this area until her death.

On her 80th birthday, Miss Porter told an interviewer: "I have a good constitution and a heart like an ox. It scares me -- I wonder how much it will take to kill me. I wouldn't want to live to be 97. But if I'd died 10 years ago, I would have missed some of the pleasantest experiences of my life. I'll hang on 'till 90 and see how it goes."

Against the day of her death, Miss Porter several years ago ordered a plain pine coffin with brass fittings from a firm in Arizona. She kept it in her house and planned to have it painted in the Mexican fashion.

Miss Porter was married and divorced three times. She leaves no immediate survivors.