Klee, an expert on the hallucinogenic drug lysergic acid diethylamide, or LSD, died Sunday of complications from surgery at the University of Maryland St. Joseph Medical Center in Towson, north of Baltimore, The Baltimore Sun reported.
The psychiatrist made headlines in 1975 when he confirmed the University of Maryland School of Medicine's Psychiatric Institute was involved in giving LSD to hundreds of soldiers between 1956 and 1959.
"They were mostly enlisted men -- there were a few commissioned officers -- but they were mostly unlettered and rather naive," Klee said. "Now the people knew they were volunteering, the bonus was leave time -- seeing their girlfriends and mothers and that kind of thing. They had a lot of free time, and most of them enjoyed it."
Klee said he experimented with the drug before the experiments started.
"I figured that if I was going to study this stuff, then I've got to experience it myself," he said. "I felt obliged to take it for experimental reasons and also because I didn't think it would be fair to administer a drug to someone else that I hadn't taken myself."
Klee was director of the Division of Adult Outpatient Psychiatry at the University of Maryland from 1959 to 1967 and served a similar role at Temple University from 1967 to 1970. He worked as a medical educator and taught at the University of Maryland, Temple and Johns Hopkins and maintained a private practice until he retired in 2000.
Klee, who was born Jan. 29, 1927, and raised in New York, is survived by two sons, three daughters, a brother and 11 grandchildren.