Henry Harris, 78, a retired chief supervisory technologist and administrative aide in the radiology department of the old Freedmen's Hospital, died Monday at his Washington home. He had cancer.

A native of Valdosta, Ga., Mr. Harris studied tailoring at Hampton Institute in Virginia and worked as a tailor in Valdosta before moving here in 1931.

He then joined Freedmen's Hospital, now Howard University Hospital, and worked as a waiter for two years. He then became an orderly, and then a technologist. He was chief supervisory technologist in the department when he retired in 1971.

Mr. Harris was said to be the first black to be admitted to the D.C. Society of X-Ray Technicians. He joined the society in 1951 and was elected treasurer the following year.

He wrote a history of Freedmen's Hospital, which was published in the society's journal, as well as scientific papers in the field of radiologic technology.

Mr. Harris was a member emeritus of the American Society of Radiologic Technologists and the D.C. Society of Radiologic Technology. In 1957, he served on the property committee of the International Conference of Radiologic Technologists.

He was a member of Asbury United Methodist Church here.

Survivors include his wife, the former Virginia Argrett, of Washington; a daughter, Maude H. Callahan of Annapolis; a sister, Willie Mae Wilcox of Messillon, Ohio, and four grandchildren.