An obituary in Wednesday's editions of The Washington Post about Helen Ryan O'Brien, 77, a potter and a retired official of the Agriculture Department who died of cancer March 5, failed to state the correct number of her surviving grandchildren. She had four grandchildren.

Helen Ryan O'Brien, 77, a retired information specialist with the Department of Agriculture who was active in Washington art circles for many years, died of cancer Thursday at the Washington Hospital Center.

Mrs. O'Brien was born in Philadelphia and studied at the Academy of Fine Arts there. In 1930, she married Robert E. O'Brien, who became a professional Army officer and who is now a retired lieutenant colonel. The family settled in this area in 1946 when he was ordered to the Pentagon.

In the late 1940s, Mrs. O'Brien wasa founder of the old Artist Mart on Wisconsin Avenue. She studied at the old Institute of Contemporary Arts here and in the early 1950s owned a gallery that specialized in prints. For herself, she was a potter and one of her pieces is inthe permanent collection of the Smithsonian Institution.

In 1954, she went to work at Agriculture and was an information officer at the time of her retirement in 1969.

She was a member of Artists Equity and the Kiln Club. Since her retirement, she had donated time to the Folger Library to help hang some of its art shows.

Her marriage to Col. O'Brien ended in divorce.

Survivors include one daughter, JaneO'Brien of San Diego, Calif., one sister, Mrs. William Watson of Merion, Pa., and three grandchildren. A son, Christopher, died in infancy.