Studies of journal citation patterns suggest that specialty areas within disciplines may be the most appro priate structural units for understanding the social organization of science. Citation studies necessarily are limited to scientists who publish, however, and studies of all members of particular disciplines would provide more general specialty structure data. Accordingly, this research applied factor analytic procedures previously used in studies of the structure of specialization among psychologists to all members of the Population Association of America. Four principal components derived from the self-designated specialties of these population scientist were rotated to a final solution by the varimax procedure and were interpreted as measuring, respectively,Social Emphasis, Geographic Emphasis, Formal Emphasis, andEpidemiological Emphasis. These results partially confirm the distinction sometimes made by population scientists between social demography and formal demography, but suggest this typology is incomplete. The results also illustrate techniques that could provide a useful alternative to citation analysis for researchers studying specialty structures in other disciplines.