Dr. Milldred Waters Dean, 77, a former teacher of mathematics at colleges in New York and volunteer with the American Cancer Society i the Washignton area, died Friday at her home in Takoma Park. She had heart and lung aiments.

Dr. Dean, who was born in Baltimore, graduated from Goucher College. She earned master's and doctoral degrees in mathematics at Johns Hopkins University.

In 1927, she married Charles E. Dean. The couple lived in Bayside and Great Neck on Long Island, N. Y., until 1963, when they moved to Takoma Park. From about 1944 until 1950, Dr. Dean taught mathematics at Hunter and Queens colleges in New York City and at Adelphi and Hofstra colleges on Long Island.

In 1968 and 1969, she was a volunteer in the accounting office of the American Cancer Society here. She also was a member of the Forum for Professionals and Executives, a study group.

In addition to her husband, of Takoma Park, survivors include a son, Robert W. of Chicago; a daughter, Margaret D. Vogel of Potomac; a sister, Ruth W. Onions of Baltimore, and seven grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the American Cancer Society.