The objectives of this study were to discover the AIDS knowledge, risk behaviors, and condom use of four groups of female professional sex workers (n = 614). Personal interviews were conducted with women working in low-price brothels, mid-price and high-price houses, and tourist areas. Only 51% of women in the low-price brothels had heard of AIDs, although most of the women in the other groups had heard of it. Knowledge of transmission and symptoms was weak in all groups, and most women were unaware of asymptomatic transmission. Most women felt safe from HIV due to ineffective strategies such as taking medications or client selection practices. Condom use with clients varied widely by group. Women in the low-price brothels reported the lowest levels of use (19% of encounters in the previous week), with women from the mid- and high-price groups reporting higher levels (68% mid-price; 71% high-price). Women working in the tourist areas reported the highest levels of use (90%). Interventions for each group need to reflect these differences in knowledge as well as the contexts of their work; important contextual factors to consider include the level of AIDS and STD knowledge in their environment, the characteristics of the clients served, and the degree of supervision that they receive.