A study of 108 femalesex workers engaged in prostitution in Georgetown, Guyana, was made in April 1993. Based on interviews and procurement of blood samples, the study investigated relationships between HIVseroprevalences and AIDSknowledge, risk behaviors, client characteristics, and condom use. Street-walkers-as distinct from sex workers in bars, hotels, and Port Georgetown-tended to charge less, be worse off socioeconomically, and have clientswho were similiarly disadvantaged; they were therefore classified as belonging to a "lower" socioeconomic stratum, while the other workers were classified as belonging to a "higher" stratum. The overall HIV seroprevalence found among the sex workers was 25 percent (95 percent CI 17 percent-33 percent). But the 50 subjects in the lower stratum had a relatively high seroprevalence (42 percent, as compared to 10 percent among those in higher stratum), accounting for 21 of the 27 HIV-seropositive subjects. Reported patterns of client origins (Guyanese or foreign), worker willingness to have sex without a condom, and condom use by clients differed by stratum. Participants in the higher stratum were more disposed to having sex without a condom. The workers' knowledge of what causes AIDS and how HIV is transmitted was low in both strata; substantial numbers of workers of workers said they had contracted a sexually transmitted disease within the past two years or were users of illicit drugs. Condom use is reportedly less common among Guyanese than foreign clients, suggesting a greater risk of contracting HIV from Guyanese clients or infecting Guyanese clients with it. The HIV seroprevalence among workerswho said they had only Guyanese clients was statistically greater than the rate among those who said they had only foreign clients. The HIV seroprevalence among those reporting more than five clients per week was statistically greater than among those reporting fewer. HIV seropisitivity was relatively high among the 12 workerswho said they used cocaine. Overall, the findings supported the view that interventions targeted at femalesex workers and their clients should be strengthened-more specifically, that concerted efforts should be made to intensify condom promotion, distribution, and social marketing; to improve STD services that provide treatment and counseling for femalesex workers; and to increase educational activities among the workers' Guyanese clients (AU)