CHICAGO, OCT. 24 -- Doctors believe a St. Louis teen-ager who died in 1969 was infected with the virus that causes AIDS, 10 years before the first AIDS cases appeared in male homosexuals in New York City, the Chicago Tribune reports in its Sunday editions.

Doctors were so perplexed by the death of the 15-year-old patient, identified as Robert R., that some of them saved samples of his body fluids and tissues for nearly two decades, hoping to find the reasons for his death, the newspaper said.

Tests on the samples by Dr. Robert Garry of Tulane University Medical School showed with near certainty that the AIDS virus was present, said a colleague at Tulane, Dr. Arthur Gottlieb.

"There's no question that it's positive," Gottlieb said. However, he said tests will be repeated this week to add to the evidence.

The test determining an AIDS link in Robert R.'s case was first announced last month at the 11th International Congress of Lymphology in Vienna, the Tribune said.

Robert R. died on May 16, 1969, about 10 years before doctors recorded what they thought were the first U.S. AIDS deaths in New York, the Tribune said. Most researchers believe the AIDS virus assumed its present form in Central Africa and arrived in the United States in the mid-1970s.

Robert R.'s death creates questions about the way AIDS was spread in the United States and over what length of time. He told doctors he had never traveled out of the Midwest.

Dr. William Drake, a pathologist who performed an autopsy on Robert R., found small, purplish lesions identified in the autopsy report as Kaposi's sarcoma, a rare form of cancer now considered an almost certain signal of AIDS.

The patient also had a sexually transmitted disease -- chlamydia -- with almost no evidence his immune system was blocking its spread.

"The case sure was consistent with some kind of virus knockdown of the immune system," Dr. Drake said.

Robert R. did not give an extensive medical history to his doctors.

"He was not a communicative individual," said Dr. Memory Elvin-Lewis, a microbiologist at Washington University in St. Louis who watched the patient's decline for more than a year.

According to the autopsy report, Robert R. "dated his physical disability from an instance of sexual relations with a neighborhood girl" in St. Louis. While he was never asked about homosexuality, evidence suggests "he could have been a male prostitute," said Dr. Marlys Hearst Witte, a University of Arizona professor of surgery who was closely involved with the case.