1. Health Services and Evaluation Branch, Division of STD Prevention, National Center for HIV, STD and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Ga,
2. Center for Health Studies, Group Health Cooperative, Seattle, Wash, and Department of Epidemiology, School of Public Health and Community Medicine, University of Washington, Seattle, Wash
3. Integrated Group Practice Quality Department, Group Health Cooperative, Seattle, Wash
4. Center for Health Studies, Group Health Cooperative, Seattle, Wash
5. Health Services and Evaluation Branch, Division of STD Prevention, National Center for HIV, STD and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Ga