Helen L. Witmer, 81, the director of research in the Children's Bureau of the Department of Health, Education and Welfare from 1952 until her retirement in 1965, died of a brain tumor Tuesday at the Carriage Hill Nursing home in Arlington.

Dr. Witmer was born in Lansford, Pa., and grew up in Lancaster, Pa. She graduated from Dickinson College and then earned master's and doctoral degrees in sociology at the University of Wisconsin. She also did postdoctoral work at the London School of Economics and earned a certificate in social work from Bryn Hawr College.

She taught in the public high schools of Reading and Lancaster, then from 1929 to 1949, she was director of research at the Smith College School of Social Work.

In 1949, she came to Washington as chief of fact-finding for the Mid-Century White House Conference on Children.

She joined the Children's Bureau shortly afterward and became director of research in 1952.

Dr. Witmer wrote and edited numerous articles on sociology and was the author of several books.

Survivors include two sisters, Eleanor M. Witmer of New York City, and Patty Gregory of the home in Alexandria, and a brother, Richard Witmer, also of the home.