This study assessed prevalence and associated factors of hypogonadism among 491 HIV-infected Thai men who visited the HIV outpatient clinic. All participants were interviewed and data were collected from medical records, including demographic and HIV-related illness characteristics. They also completed questionnaires relevant to hypogonadal symptoms, sexual function and depression. All participants' blood samples were obtained to check for total testosterone, sex hormone-binding globulin (SHBG) and albumin levels, and free testosterone (cFT) was calculated. Hypogonadism was diagnosed if a cFT level of <0.225 nmol/L was detected. The median age of the participants was 37 years old (ranging from 34 to 44 years old). HIV infection was diagnosed for a median of 77 (47-99) months. Eight of 491 participants (2%) had hypertension and 1% had diabetes mellitus (DM). Fourteen (3%) used methadone and 23% had SHBG level over 70 nmol/L. Of the 491 participants, 123 (25%) men were diagnosed with hypogonadism. The univariate analyses indicated that DM, hypertension, methadone use, SHBG level >70 nmol/L group and lack of antiretroviral therapy were associated with hypogonadism. In multivariate analysis, a SHBG level >70 nmol/L was the only factor that was significantly associated with hypogonadism (odds ratio [OR] = 1.922, P = 0.007).