Dorothy Gaffney Mullikin, 73, a retired children's librarian with the D.C. public library system, died Tuesday at George Washington University Hospital after a long illness.

Born in Golden Valley, Minn., she graduated from the University of Minnesota, where she majored in English literature, and received a graduate degree in library work from Case Western Reserve University.

Mrs. Mullikin traveled around the Mesabi Iron Range territory of Hibbing, Minn., with bookmobiles before coming here in 1927 as a reference librarian in the children's room of the old D.C. Central Library.

In 1932, she became adviser to adults in children's literature under a new program. She was considered an authority on children's books and advised parents, writers and illustrators as well as ocunties in the area that were beginning their own library systems.

Mrs. Mullikin resigned in 1942, but returned in 1957 as a children's librarian in D.C. library branches.

Later, she headed the children's library extension service, selecting books for and working with children at what was then the Glenn Dale Tuberculosis Sanitarium and at the Christ Child Convalescent Home and D.C. General Hospital. She also was an adviser to other institutions and wrote book reviews.

After retiring three years ago, Mrs. Mullikin was a volunteer with the Montgomery County Historical Society and the Rockville Public Library.

She was the widow of Thomas J. Mullikin, a lawyer, Naval intelligence agent and National Symphony Orchestra member, who died in 1958.

She is survived by a daughter, Ellen Dudley, of the home in Rockville: a sister, Mary Raymond, of Fort Lauderdale, Fla., and two grandchildren.

The family suggests that expressions of sympathy may be in the form of contributions to Children's Hospital.