Effective cognitive-behavioral therapies for insomnia have been developed over the past 2 decades, but they have not been systematically evaluated in some clinical settings. While insomnia is common among veterans with mental health problems, the availability of effective treatments is limited. We report on the group application of a cognitive-behavioral therapy for chronic insomnia in a veteran population with significant comorbidity for both psychiatric problems and chronic medical conditions. Outcome measures were obtained for both sleep (via sleep diaries) and daytime functioning. Substantial posttreatment improvements were evident for measures of sleep consolidation, total sleep time, depression, anxiety, and fatigue. The unique suitability of the group therapy approach with this population is discussed. Controlled evaluations of the group cognitive-behavioral treatment for comorbid insomnia in this and other ambulatory settings are warranted. (Contains 2 tables.)