William B. Mehler, 73, a retired senior vice president with the American Security and Trust Co, died of cancer Wednesday at Arlington Hospital.

He began his banking career as runner with the District National Bank in 1923 and later rose to assistant vice president after the name was changed to City Bank.

Mr. Mehler joined the Columbia National Bank in 1946 as an assistant vice president. Columbia was taken over by American Security Trust later that year. He served in various branches of American Security, was made a vice president in 1964 and moved to the main office four years later. He retired five years ago.

A third-generation Washingtonian, Mr. Mehler was a graduate of Central High School and Georgetown University. He attended Benjamin Franklin University, the graduate school of banking of Rutgers University and American University.

He was active in many business and civic organizations. He had served as an officer of the Washington Chapter of the American Institute of Banking and the D.C. Bankers Association. He was a former director of the Better Business Bureau and a member of the Advisory council for the D.C. Department of Vocational Rehabilitation.

Mr Mehler was a former officer of the Cleveland Park Businessmen's Association, the Georgia Avenue Businessmen's Association and the North-east Businessmen's Association. He belonged to the Metropolitan Washington Board of Trade for many years.

He had served as president of the Columbia Lighthouse for the Blind, Inc., as chairman of various divisions in the Community Chest and United Givers Fund drives and as a Red Cross instructor and air raid warden during World War II.

Mr. Mehler was a Mason, a former Republican precinct chairman and a former vestryman of St. George's Episcopal Church in Arlington. He was on the advisory committee of the National Society of the DAR. He belonged to the National Aviation Club.

He is survived by his wife, Katherine Godwin Mehler, of the home in Mclean six daughters, Dorothy Lea, of Prime Frederick Md, Charloute A. Vole, of St. Petersburg Beach, Fla., Louis Pociask, of Arlington, Carolyn Bend of Sterling, Va., Anne Mehler DuBose, of McLean, and Marison L. Embors of Belair, a son, William P. of Ft. Eastis, Va.; a brother, Charles L., 20 grandchildren and four great-grandchildren.