This cross-sectional study describes the baseline prevalence and correlates of common bacterial and viral sexually transmitted diseases (STDs) and risk behaviors among individuals at high risk for HIV recruited in five low- and middle-income countries. Correlations of risk behaviors and demographic factors with prevalent STDs and the association of STDs with HIV prevalence are examined. Between 2,212 and 5,543 participants were recruited in each of five countries (China, India, Peru, Russia, and Zimbabwe). Standard protocols were used to collect behavioral risk information and biological samples for STD testing. Risk factors for HIV/STD prevalence were evaluated using logistic regression models. STD prevalence was significantly higher for women than men in all countries, and the most prevalent STD was Herpes simplex virus-type 2 (HSV-2). HIV prevalence was generally low (below 5%) except in Zimbabwe (30% among women, 11.7% among men). Prevalence of bacterial STDs was generally low (below 5% for gonorrhea and under 7% for syphilis in all sites), with the exception of syphilis among female sex workers in India. Behavioral and demographic risks for STDs varied widely across the five study sites. Common risks for STDs included female gender, increasing number of recent sex partners, and in some sites, older age, particularly for chronic STDs (i.e., HSV-2 and HIV). Prevalence of HIV was not associated with STDs except in Zimbabwe, which showed a modest correlation between HIV and HSV-2 prevalence (Pearson coefficient = .55). These findings underscore the heterogeneity of global STD and HIV epidemics and suggest that local, focused interventions are needed to achieve significant declines in these infections.