Objective: This study examined the prevalence of insomnia and its psychosocial correlates among college students in Hong Kong. Participants: A total of 529 Hong Kong college students participated in the study. Methods: Participants completed a self-reported questionnaire that included the Pittsburgh Sleep Quality Index (PSQI), the Revised Life Orientation Test, the Perceived Stress Scale, and the Beck Depression Inventory, and questions about sociodemographic and lifestyle factors. A PSQI global score equal to or greater than 5 indicated insomnia. Results: Results indicated that 68.6% of the participants were insomniacs. Adjusted regression analyses revealed that optimism, stress, and depression significantly predicted insomnia (p less than 0.01). Conclusions: These results suggest that insomnia is very common among Hong Kong college students and associated with other psychosocial factors. This study provides preliminary data on sleep quality and risk factors for insomnia, which may be used to guide sleep hygiene promotion and intervention among college students. (Contains 4 tables and 1 figure.)