Lawrence W. Douglas, a former commonwealth's attorney of Arlington County and then a banker and lawyer in Arlington, died of cancer Aug. 23 at Northern Virginia Doctors Hospital.

Mr. Douglas was elected commonwealth's attorney in 1932 and held the post until 1948, when he entered private practice. At the same time, he was elected to the board of the Arlington Trust Co., where he served for two years. He was elected to the board again in 1954 and remained on it until 1958, when he was elected president of the bank. He held that post from 1958 to 1959, when he returned to the board. He retired from it in 1973.

In addition to his banking activities, Mr. Douglas carried on his law practice. He was a consultant to the bank, where his father had been president before him, and a practicing lawyer until shortly before his death.

Mr. Douglas was born in Arlington. He served in the Navy in World War I and saw sea duty in the Atlantic. He earned his bachelor's degree from the University of Virginia in 1922 and his law degree from Georgetown University in 1924. He was in practice in Arlington until he was elected commonwealth's attorney.

Beginning in the 1950s, Mr. Douglas spent part of his time at a family property in Waterford, Va. He later maintained a second home near Charleston, W. Va.He was a golfer and a member of the Washington Golf and Country Club.

Survivors include his wife, Ida Poor Douglas, and a daughter, Laurie, both of the home in Arlington; a brother, E. Lee Douglas, of Waterford, and three sisters, Ruth Douglas Hazel, of Broad Run, Va., Mrs. Garland Kendrick, of Arlington, and Bessie Pellern, of Benedict, Md.

The family suggests that expressions of sympathy be in the form of contributions to a church or charity of one's choice.