Objectives The sexual behaviour of men who have sex with men (MSM) in southern Africa has been little studied. We present here the first data on bisexual partnerships and bisexual concurrency among MSM in Malawi, Namibia and Botswana.

Methods A cross-sectional probe of a convenience sample of 537 men who have ever reported anal sex with another man using a structured survey instrument and rapid-kit HIV screening.

Results 34.1% of MSM were married or had a stable female partner, and 53.7% reported both male and female sexual partners in the past 6 months. Bisexual concurrency was common, with 16.6% of MSM having concurrent relationships with both a man and a woman. In bivariate analyses, any bisexual partnerships were associated with lower education (OR 1.6, 95% CI 1.1 to 2.3), higher condom use (OR 6.6, 95% CI 3.2 to 13.9), less likelihood of having ever tested for HIV (OR 1.6, 95% CI 1.1 to 2.3), less likelihood of having disclosed sexual orientation to family (OR 0.47, 95% CI 0.32 to 0.67) and being more likely to have received money for casual sex (OR 1.9, 95% CI 1.3 to 2.7). Bisexual concurrency was associated with a higher self-reported condom use (OR 1.7, 95% CI 1.0 to 3.1), being employed (OR 1.8, 95% CI 1.2 to 2.9), lower likelihood of disclosure of sexual orientation to family (OR 0.37, 95% CI 0.22 to 0.65) and having paid for sex with men (OR 2.0, 95% CI 1.2 to 3.2).

Conclusions The majority of MSM in this study report some bisexual partnerships in the previous 6 months. Concurrency with sexual partners of both genders is common. Encouragingly, men reporting any concurrent bisexual activity were more likely to report condom use with sexual partners, and these men were not more likely to have HIV infection than men reporting only male partners. HIV-prevention programmes focussing on decreasing concurrent sexual partners in the African context should also target bisexual concurrency among MSM. Decriminalisation of same-sex practices will potentiate evidence-based HIV-prevention programmes targeting MSM.