Berkeley - Lucien Le Cam, one of the handful of men who developed the modern theory of statistics, died April 25 at Doctor's Medical Center in San Pablo at the age of 75.

Le Cam, an emeritus professor of statistics and mathematics at the University of California, Berkeley, succumbed from a liver problem he developed within the past year.

Le Cam joined the UC Berkeley statistics department in the 1950s, when the department was known around the world for its mathematical approach to the field of statistics. Famed statistical pioneer Jerzy Neyman, who built UC Berkeley's eminence in the field, had embarked on a plan to provide a rigorous mathematical basis for statistical methods that, at the time, were used primarily in agriculture and government.

In providing this foundation, Neyman and colleagues like Le Cam allowed the spread of statistical methods throughout the sciences and engineering. Today, these methods are applied in nearly all fields, from sequencing the human genome and image analysis to assessing the reliability of computer systems.

Neyman invited Le Cam to join his Berkeley Statistical Laboratory in 1952, where in quick succession Le Cam obtained a PhD and joined the mathematics faculty in 1953. Le Cam has been a member of the Department of Statistics since 1955, when it was first formed with Neyman as chair. Le Cam also served as chair of the department from 1961 to 1965.

Le Cam's research concentrated on statistical methods called "asymptotic" methods, which are used to analyze very large amounts of data. His work provided a firm, rigorous foundation for the field.

"Lucien was the principal architect of the modern asymptotic theory of statistics, and one of the most important statisticians in this century," said one of his former students and a long-time collaborator, Grace Yang, professor of statistics at the University of Maryland, College Park. "He did very abstract but very fundamental work used broadly throughout the entire field of statistics."

Le Cam compiled his many ideas into a book, "Asymptotic Methods in Statistical Decision Theory," that was far ahead of its time, Yang said. The 742-page book, published in 1986, has been studied widely throughout the world.

Despite his emphasis on the fundamentals of statistics, Le Cam liked to ground himself in real world problems. This served him well when his teenage daughter came down with a rare bone cancer, osteosarcoma, and the preferred treatment failed. His research turned up an experimental therapy being tried in San Francisco, and he got his daughter admitted to a clinical trial. The new therapy worked, and Le Cam ended up collaborating with the physicians as their statistician, eventually becoming an expert on therapies for the disease.

Also, at age 23, he introduced a technique called the "characteristic functional" to study the spatial and temporal distribution of rainfall and its relation to stream flow, resulting in a model known as "Le Cam's model" in hydrology.

Le Cam loved working with students, continuing to mentor them until the time he fell ill.

"His door was always open, and he was very generous with his time," Yang said.

Le Cam was born in Croze Creuse, France, on Nov. 18, 1924, and attended the University of Paris, where he obtained his Licence es Sciences in 1945. After graduate studies in Paris, he worked as an applied statistician for Electricite de France in Paris from 1945 to 1950. He moved permanently to UC Berkeley in 1950, leaving only once, from 1972 to 1973, to serve as director of the Centre de Recherches Mathematiques at the Universite de Montreal. Though he retired in 1991, he remained active in the department until the day he became ill.

During his career, he traveled widely giving invited lectures. He was elected to the New York Academy of Sciences, the Societes de Mathematique of France and Canada, the American Academy of Arts and Sciences and the American Association for the Advancement of Science. He served as president of the Institute of Mathematical Statistics in 1973.

He received an honorary degree in 1998 from the Institute of Statistics, University of Brussels, Belgium. He also was a member of the International Statistical Institute, the American Mathematical Society and the American Statistical Association.

Upon his retirement from UC Berkeley, he was awarded the prestigious Berkeley Citation.

He is the author or editor of 10 books, included two editions of the "Berkeley Symposium on Mathematical Statistics and Probability," which he co-edited with Jerzy Neyman. He completed two books the week before his death, one a revision of his 1990 book with Grace Yang, "Asymptotics in Statistics: Some Basic Concepts."

A resident of Kensington, Calif., Le Cam is survived by his wife of 48 years, Louise Romig Le Cam; his daughter, Linda Le Cam, of Santa Barbara; two sons, Denis of Washington, D.C., and Steven of Reno, Nev.; and a brother, Jean Le Cam, of Felletin, France.

A ceremony in remembrance of Le Cam is planned for early fall at UC Berkeley.