Objectives: Translation and psychometric evaluation of a Thai version of the Medical Outcomes Study HIV Health Survey (MOS-HIV) in Thailand.  Methods: A cross-sectional survey in Chiang Mai province, northern Thailand, with data collected in face-to-face interviews using a structured questionnaire designed to measure 10 scales of quality of life (QOL). We recruited 200 people with HIV/AIDS attending self-help groups in the municipal area. Standard guidelines were followed for questionnaire translation and psychometric evaluations.  Results: Item-level internal consistency and discriminant validity were reasonably established. Success rates were 93.8 and 97.4%, respectively. Scale-level internal consistency reliability of multi-item scales was satisfactory, ranging from 0.74 to 0.88, with all exceeding inter-scale correlations. Principal components analysis of item and scale scores identified two hypothesized dimensions of the MOS-HIV. The mental health component was strongly loaded by health distress, mental health, vitality and cognitive function scales, and physical health by role, physical and social functions, and pain scales. Respondents manifesting symptoms or reporting worsening health status scored significantly lower on all scales.  Conclusions: These preliminary studies have shown the Thai version of the MOS-HIV to have psychometric properties comparable with those reported in previous surveys. Further testing and modification should make it useful as an HIV-specific QOL measure in Thailand.