William Alonso, Richard Saltonstall Professor of Population Policy at the School of Public Health and a member of the Department of Sociology in the Faculty of Arts and Sciences, died Feb. 11, at Beth Israel Deaconess Medical Center. He was 66.

A regional planning scientist, Alonso studied the dynamics of demographic change, especially concerning population problems in highly urbanized regions. Among his varied academic interests were topics such as Third World urbanization and health; European urban- regional migration patterns; and statistical investigations of race and ethnicity in American society.

Born in Buenos Aires, Alonso began his career with a bachelor's degree in architectural science from Harvard in 1954. He also received a master's degree in city planning from Harvard in 1956 and a doctorate in regional science from the University of Pennsylvania in 1960.

In his early career, he worked as director and professor in the Department of Regional and Urban Planning at the Bandung Institute of Technology in Indonesia from 1960 to 1961. He then served as a visiting professor at the Universidad Central de Venezuela in 1962 before coming to Harvard as the acting director of the Center of Urban Studies from 1963 to 1965. Alonso also worked at Yale University, the University of California at Berkeley, and Stanford University.

Alonso returned to Harvard in 1976, when he became the director of the Center for Population Studies and was named the Richard Saltonstall Professor of Population Policy. From 1983 to 1984 he served as the acting chairperson of the Department of Sociology.

In addition to his academic work at Harvard, Alonso was a consultant and adviser to numerous institutions, including the U.S. departments of Commerce, Agriculture, and Housing and Urban Development, the World Bank, the U.N. Fund for Population Activities, and the Ford Foundation.

He leaves his wife, Cornelia; a son, Lucas; a daughter, Alicia Alonso Matos; a stepson, Ghazi Al-Marayati; his mother, Joan Evans de Alonso; two brothers, Ramon and Juan; and a grandson.