The cause was cancer, said his agent, Margaret Connolly.

Guy Hamilton, the lead character of "The Year of Living Dangerously," was loosely based on Mr. Koch's younger brother, Philip, a reporter for the Australian Broadcasting Commission who covered the violent decline of the regime of President Sukarno of Indonesia in the 1960s.

In Mr. Koch's narrative, Hamilton's personal life and his work as a journalist become entangled with people whose identities and loyalties are slowly revealed to be more complicated than he expected — echoing the mystery with which many Australians regarded Asia and its political turbulence at the time.

The book was published in 1978. The film, whose screenplay Mr. Koch (pronounced kosh) co-wrote, was released in 1982, with Mel Gibson in the starring role. (Mr. Gibson's tense signoffs to his radio dispatches — "This is Guy Hamilton in Jakarta" — are remarkably similar to those of Philip Koch, some of which are available online.)

The film, directed by Peter Weir, also stars Sigourney Weaver, as a British spy and Mr. Hamilton's romantic interest, and Linda Hunt, who won an Academy Award for her portrayal of Hamilton's male cameraman and mentor, Billy Kwan.

The book initially received little attention outside Australia, but the film's success brought Mr. Koch new acclaim, both at home and internationally. His work was often cited as helping Australia to shift its cultural focus from its Western ancestors in Britain and Ireland toward its increasing engagement with Asia.

Two of his later novels, "The Doubleman," and "Highways to a War," which was based loosely on the life of the Vietnam War photographer Neil Davis, won the Miles Franklin Award, Australia's highest literary honor.

Christopher John Koch was born on July 16, 1932, in Hobart, on the southern Australian island of Tasmania. His father, Burton, an accountant, and his mother, Phyllis, were concerned about him when he dropped out of school and was later reprimanded for reading too much while working in a bookstore. He eventually graduated with honors from the University of Tasmania with degrees in English and philosophy.

He worked as a radio producer for the Australian Broadcasting Service in Sydney for many years before devoting himself full time to writing, starting in 1972.

Survivors include his wife, Robin; a son, the classical guitarist Gareth Koch, from an earlier marriage that ended in divorce; his brother, Philip; and a sister, Susan.

He published his first novel, "The Boys in the Island," in 1958, which helped him win a creative writing fellowship to Stanford a few years later. The book was a coming-of-age story about a young man growing up in Tasmania but dreaming of moving to the mainland.

Mr. Koch and the characters in many of his books frequently migrated between Tasmania and the rest of the world. In Mr. Koch's case, he moved back and forth to Sydney several times before he settled in Tasmania in the town of Richmond, outside Hobart.

"It's the eternal circle, to escape and to return," he told The Hobart Mercury in 1995. "It's the penalty for being an islander."