In 30 conscious patients (24 men, 6 women) aged 30-74 years suffering from ischemic lesions in the cerebral hemispheres, polygraphic night sleep recordings were performed about 45 days after the beginning of the illness. The alterations in sleep were characterized by a delay in the onset of sleep, prolonged waking periods, and a reduction of deep synchronous sleep. Statistical analysis revealed a relationship between prolonged waking time with higher age as well as with high complex reaction time and euphoric state of mind, which can be considered as a sign of psycho-organic impairment. In contrast thereto, the degree of the neurological symptomatology is of less importance for the kind and extent of the sleep disturbances.