Background: Men who have sex with men (MSM) are highly vulnerable to HIV infection, but this population can be particularly difficult to reach in sub-Saharan Africa. We aimed to estimate the number of MSM who sell sex in and around Mombasa, Kenya, in order to plan HIV prevention research.
Methods: We identified 77 potential MSM contact locations, including public streets and parks, brothels, bars and nightclubs, in and around Mombasa and trained 37 MSM peer leader enumerators to extend a recruitment leaflet to MSM who were identified as ‘on the market’, that is, a man who admitted to selling sex to men. We captured men on two consecutive Saturdays, 1 week apart. A record was kept of when, where and by whom the invitation was extended and received, and of refusals. The total estimate of MSM who sell sex was derived from capture–recapture calculation.
Results: Capture 1 included 284 men (following removal of 15 duplicates); 89 men refused to participate. Capture 2 included 484 men (following removal of 35 duplicates); 75 men refused to participate. Of the 484 men in capture 2, 186 were recaptures from capture 1, resulting in a total estimate of 739 (95% confidence interval, 690–798) MSM who sell sex in the study area.
Conclusions: We estimated that 739 MSM sell sex in and around Mombasa. Of these, 484 were contacted through trained peer enumerators in a single day. MSM who sell sex in and around Mombasa represent a sizeable population who urgently need to be targeted by HIV prevention strategies.