Objective: Poor sleep is known to cause detrimental effects on the course of diverse psychiatric disorders and is a putative risk factor for hostility and aggression. Thus, sleep may be crucial in forensic psychiatric practice. However, little is known about the prevalence of sleep disturbances in these complex psychiatric patients. Methods: In this study we investigated the presence of sleep disorders and subjective sleep quality using the Sleep Diagnosis List (SDL), the Pittsburgh Sleep Quality Index (PSQI), interviews addressing the causes of sleep complaints, and file information on sleep medications in 110 patients admitted to a forensic psychiatric hospital. Results: Almost 30% of the participants suffered from one or more sleep disorders, especially insomnia. An even larger proportion of the participants (49.1%) experienced poor sleep quality. Interestingly, patients with an antisocial personality disorder or traits were particularly dissatisfied with their sleep. The most common causes of sleep problems were suboptimal sleep hygiene, stress or ruminating, negative sleep conditioning, and side effects of psychotropic medication. Of the poor sleepers, 40.7% received a hypnotic drug. Conclusion: Despite intensive clinical treatment, sleep problems are experienced by a large number of forensic psychiatric patients. It would be worthwhile to examine the effects of pharmacological and non-pharmacological sleep interventions on both psychiatric symptoms and reactive aggressive behavior in forensic patients. (C) 2013 Elsevier B.V. All rights reserved.