Sister Kathleen Mary O'Brien, 52, a member of the Sisters of Notre Dame de Namur who taught in the Washington area and elsewhere, died of leukemia Sept. 18 at the home of the Sisters of Notre Dame in Ilchester, Md.

Sister Kathleen's last mission was a pastoral ministry at Holy Trinity Church in Glen Burnie.

She was born in Haddonfeild, N.J., and grew up there, in the Washington area, where she attended the Nativity School, and in Drexel Hill, Pa. She graduated from Trinity College in Washington. She also held a degree in theology from St. Mary's Seminary in Baltimore and a master's degree from Villanova University.

She was professed a Sister of Notre Dame de Namur in 1948. Her first assignment was as a teacher at St Francis Xavier School in Washington. She later taught in Hyattsville and elsewhere in Maryland and in New York, Virginia and Pennsylvania.

Survivors include her mother, Florence G. OBrien, of Plymouth meeting, Pa., and four sisters, Anne Roth, of Hawthorne, N.J., Jo-Anne Tavenner, of Rockville, Patricia Dywer, of Blue Bell, Pa., and Jacqueline Connolly, of Bethesda.

The family suggests that expressions of sympathy be in the form of contributions to Leukemia Research, Jhns Hopkins Hospital, 600 N. Wolf St., Baltimore, Md.