Behavioral intervention for treating insomnia in breast cancer survivors. Design: Randomized controlled trial. Setting: University and medical center settings. Sample: 72 women at least three months after primary treatment for breast cancer with sleep-onset or sleep maintenance insomnia at least three nights per week for at least three months as determined through daily sleep diaries. Methods: Random assignment to a multicomponent intervention (stimulus control instructions, sleep restriction, and sleep education and hygiene) or a single-component control group (sleep education and hygiene). Main Research Variables: Sleep-onset latency, wake after sleep onset, total sleep time, time in bed, sleep efficiency, and sleep quality. Findings: After the intervention, both groups improved on sleep-onset latency, wake after sleep onset, total sleep time, time in bed, sleep efficiency, and sleep quality based on daily sleep diaries. A between-group difference existed for time in bed. Wrist actigraph data showed significant pre- to postintervention changes for sleep-onset latency, wake after sleep onset, total sleep time, and time in bed. When compared to the control group, the multicomponent intervention group rated overall sleep as more improved. Conclusions: A nonpharmacologic intervention is effective in the treatment of insomnia in breast cancer survivors. Implications for Nursing: Breast cancer survivors can benefit from a cognitive-behavioral intervention for chronic insomnia. Sleep education and hygiene, a less complex treatment than a multicomponent intervention, also is effective in treating insomnia. [Abstract for this article also available on page 943 of printed version. The full text of this article can be accessed at www.ons.org/publications/journals/ONF