Dr. Ian Stevenson, 88, who spent nearly half a century traveling the world to meticulously investigate hundreds of cases of small children who appeared to recall previous lives, died of pneumonia Feb. 8 at the Westminster-Canterbury of the Blue Ridge retirement community in Charlottesville.

To Dr. Stevenson and his many admirers, his detailed case studies provided more than ample room for, as he liked to put it, "a rational person, if he wants, to believe in reincarnation on the basis of evidence."

In 1977, the Journal of Nervous and Mental Disease devoted most of one issue to Dr. Stevenson's work. In a commentary for the issue, psychiatrist Harold Lief described Dr. Stevenson as "a methodical, careful, even cautious, investigator, whose personality is on the obsessive side." He also wrote: "Either he is making a colossal mistake, or he will be known . . . as 'the Galileo of the 20th century.' "

But with rare exception, mainstream scientists -- the only group Dr. Stevenson really cared to persuade -- tended to ignore or dismiss his decades in the field and his many publications. Of those who noticed him at all, some questioned Dr. Stevenson's objectivity; others claimed he was credulous. Still others suggested that he was insufficiently versed in the cultures and languages of his subjects to do credible investigations. Dr Stevenson responded that his critics should come investigate the cases for themselves. That did not happen.

But Dr. Stevenson himself recognized one glaring flaw in his case for reincarnation: the absence of any evidence of a physical process by which a personality could survive death and transfer to another body.

The evidence he did provide in abundance came not from past-life readings or hypnotic regressions but from using the techniques of a detective or investigative reporter to evaluate claims that a young child, often just beginning to talk, had spontaneously started to speak of the details of another life. In a fairly typical case, a boy in Beirut spoke of being a 25-year-old mechanic, thrown to his death from a speeding car on a beach road. According to multiple witnesses, the boy provided the name of the driver, the exact location of the crash, the names of the mechanic's sisters and parents and cousins, and the people he hunted with -- all of which turned out to match the life of a man who had died several years before the boy was born, and who had no apparent connection to the boy's family.

In interviewing witnesses and reviewing documents, Dr. Stevenson searched for alternate ways to account for the testimony: that the child came upon the information in some normal way, that the witnesses were engaged in fraud or self-delusion, that the correlations were the result of coincidence or misunderstanding. But in scores of cases, Dr. Stevenson concluded that no normal explanation sufficed.

Tall and lanky, patrician in appearance and diction, Dr. Stevenson was a tireless researcher who often would forget to stop for food during all-day treks on dusty third-world trails, running younger colleagues into the ground by nightfall. He catalogued more than 2,500 remarkably similar cases, mostly in Asia and the Middle East but also in Europe, Africa and North and South America. His first book on the topic, "Twenty Cases Suggestive of Reincarnation," was published in 1966; his last, "European Cases of the Reincarnation Type," in 2003.

Dr. Stevenson, a native of Montreal, earned his medical degree from McGill University in Montreal in 1943, graduating at the top of his class. In 1957, at 39, he became head of the department of psychiatry at the University of Virginia School of Medicine. But from his mother, a devotee of theosophy, which Dr. Stevenson described as a "kind of potted Buddhism for Westerners," he had inherited a keen interest in the paranormal, which became a calling after a trip to India in 1961 convinced him that the child cases were both ubiquitous and impressive.

As his research earned the scorn of some colleagues and caused unease in the university administration, Dr. Stevenson gave up his administrative duties to head what he cagily named the Division of Personality Studies, now the Division of Perceptual Studies, funded by a grant from Chester Carlson, the man who invented the Xerox process.

Dr. Stevenson retired from active research in 2002, leaving his work to successors led by Dr. Bruce Greyson. Dr. Jim Tucker, a child psychiatrist, has carried on Dr. Stevenson's work with children, focusing on North American cases.

Tucker said that toward the end of his life, Dr. Stevenson had accepted that his long-stated goal of getting science "to seriously consider reincarnation as a possibility" was not going to be realized in this lifetime.

But in 1996, no less a luminary than astronomer Carl Sagan, a founding member of a group that set out to debunk unscientific claims, wrote in his book, "The Demon-Haunted World": "There are three claims in the [parapsychology] field which, in my opinion, deserve serious study," the third of which was "that young children sometimes report details of a previous life, which upon checking turn out to be accurate and which they could not have known about in any other way than reincarnation."

His first wife, Octavia Stevenson, died in 1984.

Survivors include his wife of 21 years, Margaret Pertzoff of Charlottesville; a brother; and a sister.

Shroder, editor of the Post's Sunday magazine, wrote a book about Dr. Stevenson, "Old Souls: The Scientific Evidence for Past Lives" (1999).