The demographic characteristics of "classic" Kaposi's sarcoma (KS) and of "epidemic" KS in Los Angeles, CA, were compared with the use of data from the Cancer Surveillance Program, the population-based tumor registry in Los Angeles County. The data obtained document the magnitude of the excess risk of classic KS for Jewish men of European (especially Eastern and Southern European) origin. The data also show in a systematic way the magnitude of the increase in acquired immune deficiency syndrome-related KS in one large urban area of the United States. In addition, they demonstrate that the demographic risk factors of religion and birthplace for classic KS are unrelated to epidemic KS and that the clinical presentation in terms of stage and primary site of classic KS is distinct from that of the epidemic form of the disease.