Severe disturbances of sleep architecture and circadian rhythms are common in traumatic brain injured patients; however, complete absence of the rapid eye movement sleep stage is very rare. We describe a brain injured patient with cognitive disturbances who developed severe alterations of sleep architecture, accompanied by paranoid and jealousy delusions. Following several trials with conventional antipsychotics his psychotic state stabilized but he continued to complain of insomnia and daytime fatigue. When treated with risperidone 2 mg/day, both his sleep and the delusional thoughts improved markedly and his daytime alertness increased. Severe deterioration of his support system brought about discontinuation of treatment With re-emergenee Of all symptoms.