Chauncey Brewster Chapman Jr., 61, who retired last year as assistant solicitor for territories in the Department of Interior, died Saturday at George Washington University Hospital after a heart attack. He lived in Washington.

Mr. Chapman joined Interior in 1959 as an attorney-adviser in the office of the solicitor. He specialized in the law of public land management, particularly as it applied to forestry.

He was named assistant solicitor for territories in 1967 and later became associate solicitor for territories, wildlife and claims which became general legal services. He helped develop democratic forms of governments in the territories as well as environmental and endangered species protection laws. From 1973 until his retirement, he was assistant solicitor for territories, and during that time, as chairman of the Samoan Gubernatorial Commission, established the process for direct elections for governor of American Samoa.

At the time of his retirement, Mr. Chapman received a plaque from his friends at the Interior Department that cited him for his dedicated public service and rapport with his fellow workers. He had retired because of differences with the administration.

Mr. Chapman was born in New York City. He was a direct descendant of William Brewster who signed the Mayflower Compact. He was a graduate of Williams College. He served as a major with the 4th Marine Division in the South Pacific in World War II. He was a combat instructor and intelligence officer, who participated in three major landings, including that on Guam. Trainees included Samoan Marines and Mr. Chapman was named an honorary High Talking Chief by some of his Samoan colleagues.

After the war, he earned a degree from Georgetown University Law School and was in private practice before entering government service.

He was a member of the D.C. and American Samoan Bars, and an associate member of the Hawaiian Bar, and was of counsel to the law firm of Maas and Coleman, St. Thomas, Virgin Islands.

Mr. Chapman was a founding member of the City Tavern Club. He had served on the vestry and taught Sunday School at Christ Episcopal Church in Georgetown.

His marriage to his first wife, the former wife Charlotte Keyser, ended in divorce.

He is survived by his wife the former Patricia Lee Potter of Washington; a son, Chauncey B. 3rd of Columbia, S.C.; two daughters, Rebecca Palmer Chapman Booth of Grosse Pointe Shores, Mich., and Susan Keyser Chapman, of Bristol, England; five stepchildren, Barry Weyburn Post of Clinton, Conn., Lila Luce of Madison, Wis., H.C. Luce of Boston, and Krisztina Lee Botond and Andrew I. Botond, both of Washington; a brother Richard B., of Clinton, N.Y., and one grandchild.

The family suggests that expressions of sympathy be in the form of contributions to Federal Union Inc. in Washington.