Isaac Asimov, the prolific writer of science fact and fiction who laid down the literary laws of how robots must behave, died Monday, his brother said. He was 72.

Stanley Asimov, a vice president of Newsday, said his brother died at New York University Hospital of heart and kidney failure.Earlier this year, Asimov announced that a prostate operation had slowed him down and he was cutting back on his writing. He also suspended his monthly column in Fantasy and Science Fiction magazine, to which he had contributed some 400 columns and articles over 33 years.

Publishing 10 or more titles in a year was no big deal for Asimov, and his production had continued after a heart attack in 1977 and triple bypass surgery in 1983.

Among his nearly 500 books, three early novels known as the "Foundation" trilogy were honored in 1966 with a special Hugo Award as the best science-fiction series ever. The Hugo is science fiction's equivalent of the Pulitzer Prize or Academy Award.

Other notable novels included "The Caves of Steel" in 1954 and "The Naked Sun" in 1957, in which a police officer is teamed with a robot detective.

Robot and "Foundation" themes eventually expanded and intertwined in 14 novels. Taken together, they formed a picture of humanity in millennia to come - spread through the stars, with Earth itself all but forgotten, but the people still in the thrall of human nature.

A final novel, "Forward the Foundation," finished a few months ago, will be brought out later this year, said Lou Aronica, Asimov's publisher at Bantam Books.

Asimov was a biochemist by training, and a hallmark of his fiction was that the science, sometimes mind-boggling - like faster-than-light travel - was none-the-less convincing.

One exception, he conceded, was the popular "Fantastic Voyage" in 1966, about a medical team being miniaturized and injected into the bloodstream of a dying man.