A patient had unpleasant complex hallucinatory activity beginning 36 h postsurgery that lasted 48 h. Closing the eyes precipitated a flood of visual imagery that immediately roused the patient and prevented sleep. The imagery was predominantly visual, but there were auditory and narrative components suggesting a relationship to dreaming. An electroencephalogram showed that the hallucinatory activity was related to a recurring sequence of drowsiness, a few vertex slow waves, a myoclonic jerk, and arousal. Morphine was a prime suspect as the causative agent. The basic disturbance probably lay in the sleep-dream system. The syndrome has not been fully defined in the past.