Blind people are prone to suffer from sleep-wake schedule disorders. This report describes 2 months of monitoring of sleep patterns and aggressive behaviors in a totally blind, severely retarded adolescent boy, hospitalized in a psychiatric hospital. The documented sleep-wake patterns seem to portray a sleep-wake schedule disorder with a monthly periodicity. Aggressive behaviors seem to echo the same periodicity, suggesting that a common or linked biobehavioral timing mechanism may underlie both sleep and episodic aggressive outbursts. The need to consider sleep schedule disorders as a primary process underlying some psychopathological disorders, and the related risks of misdiagnosis and mistreatment, are highlighted.