Tibor J. "Tibi" Greenwalt, 91, a pioneer blood researcher and former national director of the American Red Cross blood program, died of congestive heart failure July 17 at Christ Hospital in Cincinnati.

Dr. Greenwalt established the rare-donor registry for the American Red Cross, where he worked from 1967 to 1978, and for the rival American Association of Blood Banks, which he helped found in 1947.

At the American Red Cross, he directed research into hepatitis and the storage of red blood cells and developed the first filter for white blood cells. As a specialist in Rh factors and hemolytic disease of the newborn, he determined that red cells work better than whole blood in certain transfusions.

"He fostered a spirit of energy, quality and inquiry within the organization and developed and trained a whole generation of leaders in the field," Roger Dodd, vice president of Red Cross blood research and development, said in a statement.

Born in Budapest, Dr. Greenwalt came to the United States at age 6. He graduated from New York University, where he received his medical degree in 1937. During World War II, he served in the Army in India, where he pursued his interest in blood diseases.

After the war, he became medical director of what is now the Blood Center of Wisconsin. He took charge of the hematology clinic at Milwaukee General Hospital and was on the faculty of Marquette University's School of Medicine.

When he moved to Washington to work for the Red Cross, he became a clinical professor of medicine at George Washington University and later was a consultant and guest lecturer at the National Naval Medical Center and the National Institutes of Health.

He moved to Cincinnati in 1979, serving as the Hoxworth Blood Center's director until 1987. He then became director of its research division until 2000. Even as an emeritus professor, he kept regular office hours daily, and he recently completed two scientific papers. He also worked out with a personal trainer twice a week until recently becoming ill.

Dr. Greenwalt was founding editor of Transfusion magazine and contributed to more than 200 major books and research papers. He was elected to the Institute of Medicine of the National Academy of Sciences in 1984. This year, he was awarded the Karl Landsteiner Memorial Award from the American Association of Blood Banks, which also named a lectureship after him.

His first wife, Margaret Hirschfeld, died in 1947. His marriage to Jean Stotzer ended in divorce. His third wife, Shirley Johnson, died in 1970; his fourth wife, Dr. Pia Glas, died in 1996.

Survivors include a son from his first marriage, Dr. Peter Greenwalt of Cleveland, and three grandchildren.

Tibor Greenwalt led the American Red Cross's blood program.