Clarence E. Dawson, 80, a retired Washington attorney, died of cancer Monday at his home in Chevy Chase.

Mr. Dawson was born in Washington and attended Central High School. He served on the Mexican Border as a member of the Maryland National Guard in 1916 and in France as a member of the Army Corps of Engineers in World War I.

He earned his law degree from Georgetown University in 1923. In the same year, he began practice as an attorney in the office of the chief counsel of the old Bureau of Internal Revenue in the Treasury Department. In 1935, he transferred to the Justice Department as a senior trial attorney in the tax division.

In 1943, Mr. Dawson joined the law firm of Milbank, Tweed, Hadley & McCloy, which is based in New York, and was the partner in charge of its Washington office until his retirement in 1970.

Mr. Dawson was a member of the D.C. and American bar associations. He was a founder of the Masonic Order of Barristers, which since has merged with the Lebanon Lodge, and a member of the Columbia Country Club and the University Club. He lived in Chevy Chase for most of his life.

Survivors include his wife, Adelaide of Chevy Chase; three children by a previous marriage, Dayl Dawson Hester of Bethesda, Marjorie Dawson Tym of Daton, Ohio, and Clifford H. Dawson of Bethesda; a sister, Thelma Collins of Quincy, Mass., and eight grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the American Cancer Society, 344 University Blvd. West, Silver Spring, 20901.