Chronic insomnia is a problem among individuals with serious mental illnesses. In an effort to expand treatment options, we examined whether well-established cognitive-behavioral treatments for insomnia developed for individuals in the general population generalize to those for people with serious mental illnesses. Individuals participated in comprehensive sleep evaluations and cognitive-behavioral therapy. Results suggest that sleep problems often began during periods of distress and/or exacerbation of illness but were maintained by environmental, behavioral, and cognitive factors. With the treatment, participants reported improvement in many sleep parameters. Initial indication is that cognitive-behavioral therapy does generalize. More rigorous research seems warranted.