BACKGROUND: Clonazepam is widely used for the treatment of posttraumatic stress disorder (PTSD)-related sleep disturbances despite very limited published data supporting its use for this indication. OBJECTIVE: We conducted a pilot-controlled trial to provide more data on this clinical practice and lay the foundation for more definitive studies. METHODS: The study was designed as a randomized, single-blind (ie, patient only), placebo-controlled, crossover clinical trial involving administration of clonazepam 1 mg at bedtime for one week followed by 2 mg at bedtime for one week. The following week served as a washout period before the alternate treatment was begun. Patients completed sleep diaries each morning upon awakening throughout the study. Parameters included quantity of sleep, quality of sleep, frequency and intensity of difficulty falling or staying asleep, and frequency and intensity of recurrent distressing dreams. RESULTS: Six patients with combat-related PTSD participated in the study. There were no statistically significant differences between clonazepam and placebo for any measure, although clonazepam therapy resulted in mild to moderate numeric improvements in difficulty falling or staying asleep. Adverse effects of clonazepam were generally mild and essentially indiscernible from those attributed to placebo. Only one patient elected to receive further treatment with clonazepam at the conclusion of the trial. CONCLUSIONS: Clonazepam therapy was largely ineffective in improving sleep disturbances, particularly nightmares, associated with combat-related PTSD. The small sample size was a significant limitation of this study, but the prospective design and single-blind, placebo-control parameters were strengths. Further studies are needed to further define the role of this widespread clinical practice.