Stephen C. Cromwell Sr., 82, who was executive director of the Maryland Department of Employment Security for six years before retiring in 1967, died of cardiac arrest Thursday at Suburban Hospital in Bethesda.

He worked for the old Maryland Emergency Relief Administration and the old Civil Works Administration for two years before becoming a district director of the old Works Progress Administration in 1935.

Two years later, he joined the Maryland Unemployment Compensation Board as its executive secretary. He later served as director of its compensation division before becoming executive director of the Department of Employment Security.

Mr. Cromwell was chairman of the Montgomery County Selective Service Board for 20 years before retiring in 1960. He also had served on the board of directors of the Montgomery County YMCA.

He had been chairman of the advisory board of the Maryland National Bank.

He had been a member of the Burning Tree and Chevy Chase country clubs and the Metropolitan Club.

Mr. Cromwell was born in Washington and reared in Rockville. He was a graduate of St. Alban's School and the University of Pennsylvania. He served as a Marine Corps officer in France during World War I.

He is survived by his wife of 57 years, Phyllis E., of the home in Silver Spring; a daughter, Phyllis E. Cromwell, also of Silver Spring; two sons, Dr. Stephen C. Jr. and James J., both of Rockville, and eight grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the Montgomery County Heart Fund in Kensington.