Alexander Long Wilson, 51 a lawyer and civil leader in Arlington County, died of cancer Tuesday at George Washington University Hospital.

He had practiced law in Arlington for the past 20 years and for the past two years had been a senior partner in the law firm of Lewis Wilson, Cowles, Lewis and Jones Ltd.

Mr. Wilson was a member of tthe executive committee of the Arlington County Bar Association, and as chairman for many years of its legal aid committee, had been primarily responsible for establishingthe Arlington County Legal Aid society Inc.

He was chairman of the legal aid committee of the Virginia State Bar and a member of the board of directors of the Legal Services Corporation of Virginia.

Mr. Wilson also belonged to the Virginia and American bar association the Northern Virgina Trial Lawyers Association and the National Legal Aid and Defenders Association.

Active in the Democratic Party in Arlington County, he at various times had been a candidate for the House of Delegates, the Arlington County Board and commonwealth's attorney.

Born in Rock Hill, S.C, Mr. Wilson was attending Episcopal High Achool in Alexandria when his family moved to this area.

In the latter part of World War II, he served in Europe with the Army Air Corps. He then attended the University of South Carolina.

He was recalled to active duty as an Army infantry officer and saw combat during the Korean conflict, when he was awarded the Bronze Star. He also served as a green beret with the 77th Special Forces Group in 1957.

He was a member of the Arlington County Junior Chamber of Commerce, the First Families of Virginia, the veterans of Foreign Wars, the Moose and the Washington Golf and County Club. He had been secretary and general counsel of the Arlington Outdoor Education Association.

He is survived by his wife, Patricia Ann Benson Wilson, and a son, Alexander L. Jr., both of the home in Arlington; his mother, mrs. York L. Wilson of Washington, and seven brothers and sisters, York L. Jr., of Aloha, Ore., Minerva Andrews, Eleanor Yarbrough and Suzanna Beckman, all of McLean, Blackburn of San Francisco, Oscar B., of Miami Springs, Fla., and Gaston Def., of Langley Park, Md.

The family suggest that expressions of sympathy may be in the form of contributions tot he Legal Aid Society of Arlington.