BACKGROUND:: Little is known about the prevalence of concurrent sexually transmitted diseases (STDs) and associated risky behaviors among patients living with HIV in Taiwan. METHODS:: A cross-sectional study was conducted using HIV-infected patients who attended the outpatient clinic of an AIDS referral center in Taiwan between August 2005 and December 2005. Participants received physical examinations, serological tests for syphilis, and urine tests for both Neisseria gonorrhoea and Chlamydia trachomatis by the polymerase chain reaction method. A self-administered questionnaire concerning sexual behaviors and history of STDs was collected. The history of repeat STDs since the diagnosis of HIV was retrieved by chart review. RESULTS:: A total of 123 HIV-infected patients were enrolled. Among these, 43.1% reported a history of STDs before the diagnosis of HIV infection. A total of 36.1% had concurrent STDs at the time of HIV diagnosis, and 8.9% were diagnosed with STDs at enrollment. Syphilis was the most common STD. The rate of condom usage for the last sexual intercourse was 68.3%, and the use of illicit/recreational drugs was 7.9%. HIV diagnosis within 3 months (odds ratio [OR], 46.5; 95% confidence interval [CI], 3.9-552.0; P = 0.002) and repeated infection with STDs since HIV diagnosis (OR, 18.7; 95% CI, 1.7-201.6; P = 0.016) were 2 independent predictors of participants with active STDs at enrollment. CONCLUSION:: HIV-infected individuals had a high rate of concurrent STDs before and after diagnosis of HIV infection. Our study findings highlight the importance of secondary prevention strategies for patients living with HIV.