In order to effectively study the population experiencing insomnia, it is important to identify reliable and valid tools to measure sleep that can be administered in the home setting. The purpose of this study was to assess psychometric properties for the Chinese version of the Pittsburgh Sleep Quality Index (CPSQI) in community-dwelling adults with primary insomnia. The CPSQI had an overall reliability coefficient of 0.82 -0.83 for all subjects. "Subjective sleep quality" was the component most highly correlated with the global score. Overall, the CPSQI showed acceptable test-retest reliability over a 14- to 21-day interval with a coefficient of 0.85 for all subjects and 0.77 for primary insomniacs. The two contrasting groups had significantly different global and component scores. A CPSQI of greater than 5 yielded a sensitivity and specificity of 98 and 55% in primary insomniacs vs. controls. A CPSQI of greater than 6 resulted in a sensitivity and specificity of 90 and 67%. Results suggest that the CPSQI is a psychometrically sound measure of sleep quality and disturbance for patients with primary insomnia. It may not be an effective screening tool because of its low specificity, but it can be a sensitive, reliable, and valid outcome assessment tool for use in community-based studies of primary insomnia.