We conducted a cross-sectional study of sexually transmitted disease and HIV infections among a random sample of the 2364 adult population in 2000 in Bobo-Dioulasso, the second largest town in Burkina Faso. The prevalence of HIV infection was 5.2%. Risk factor analysis was conducted among sexually active men 20 to 34 years old and women 15 to 24 years old. Factors independently associated with HIV infection among men were having been married (adjusted odds ratio (aOR)=8.19 [1.70-39]), reporting more than two non-marital partners in the last 12 months (aOR=6.07 [1.14-32.4]), reporting a past urban residence other than Bobo-Dioulasso (aOR =6.37 [1.96-20.7] and having a positive serology for HSV-2 infection (aOR=12.0 [3.49-40.9]). Among women the factors were being Christian (aOR=3.73 [1.20-11.6]), having had a first sexual partner more than 24 years old (aOR =4.30 [1.35-13.6]) and having a positive serology for HSV-2 infection (aOR =4.40 [1.32-14.6]). HIV infection in Bobo-Dioulasso therefore depends on both exposure factors (sexual behaviours) and transmissibility cofactors (HSV-2).