aLos Angeles County Department of Health Services, Los Angeles, CA, USA; bHealth Research Association, Los Angeles County/University of Southern California Medical Center, Los Angeles, CA, USA; and cVan Ness Recovery House, Hollywood, California, USA.
Sponsorship: This study was supported by the University of California Universitywide AIDS Research Program, grant no. PC97-LAC-012L, and the California State Office of AIDS.
Received: 23 June 2000;
revised: 31 August 2000; accepted: 11 September 2000.