OBJECTIVE: Measuring sexually transmitted infections (STIs) and sexual practices in injection drug users (IDUs) and their regular sex partners. GOAL: Informing HIV intervention programs. DESIGN: Cross-sectional. RESULTS: One percent IDUs and 2% of their regular female sex partners were syphilis infected; 40% (84/211) and 38% respectively (81/211) were infected with HSV-2. 30% IDUs and 5% of their female regular sex partners were HIV positive. Serodiscordant results for syphilis and HSV-2 were noticed. Women having first sex at age<or=17 years and those who had HIV-positive IDUs as their male sexual partner had two times the odds of having any non-HIV-STI (OR 2.04; 95% CI 1.1-3.8; P=0.02 and OR 2.38; 95% CI 1.1-5.1; P=0.02 respectively) in a multivariate model. Women>or=38 years had seven times the odds of having any non-HIV-STI. CONCLUSION: Reaching out to IDUs and their female regular sex partners with modified STI management guideline and promoting women-controlled safer sex measures are needed harm-reduction measures.