Harold O. Wyckoff, 89, a retired physicist of the National Bureau of Standards who was active in national and international radiological societies and organizations, died May 6 at the Collington Retirement Community in Mitchellville after a heart attack.

Dr. Wyckoff did work in the field of radiation measurement as amember, secretary and chairman of the International Commission on Radiological Units and Measurements.

He was the group's secretary from the mid-1950s to 1969 and then was its chairman until 1985.

He also was instrumental in introducing radiation measurement as part of the stated mission of the National Council on Radiation Protection and Measurements.

Dr. Wyckoff chaired several of the organization's committees that produced reports on radiation protection on a radiological field.

He also held various offices with the American College of Radiology and the Radiological Society of North America. He was the scientific director of the Armed Forces Radiobiology Research Institute from 1966 to 1971, a time when the institute was deeply involved in studies of radiation effects and conditions that could be found on a nuclear battlefield or after a major nuclear attack on the country.

He was born in Traverse City, Mich. After receiving bachelor's and doctoral degrees in physics from the University of Washington in Seattle, he came to Washington in 1940 and a year later joined the National Bureau of Standards.

In 1943, he was one of several people recruited by his supervisor at the bureau to join the Operations Research Division of the U.S. Army, Ninth Air Force in Europe. There, he studied aerial reconnaissance efforts and received the Bronze Star for his service.

Back at the bureau, Dr. Wyckoff was selected for a number of jobs, including chief of the X-ray Standards Section, chief of the Radiation Physics Laboratory and assistant chief of the Radiation Physics Division.

He retired from the bureau in 1966 but continued to work as a consulting radiological physicist.

His honors from the Commerce Department included a silver medal for meritorious service and a gold medal for exceptional service. In 1971, he received a medal from the Defense Atomic Support Agency for exceptional civilian service.

In his free time, he enjoyed woodworking and golf. He was a member of the Cosmos Club.

Survivors include his wife, Mildred Wyckoff of Mitchellville; two children, Jeanette M. Wyckoff of Richmond and Harold O. Wyckoff Jr. of Des Plaines, Ill.; a sister, Lola Stephens of Lake Ridge; and two grandchildren.