By 120 schizophrenic patients of the out-patient clinic or the social Psychiatric Service in Zurich, all mental hospital treatments were recorded (dates of admission and discharge). 65 patients, who became ill before 1973, were compared with 55, who first became ill after 1973. The frequency and duration of the hospitalisations were examined. Three variations were employed in the statistical comparisons, regarding: age groups (generations), time periods and a combination of both. None of these three variations showed any significant difference in frequency or duration of hospitalisation. During the first 4 1/2 years of illness, both generations were similarly frequent and long in hospital, namely, on the average, 3 months per year and once every 12 to 15 months.