OBJECTIVE To examine period trends in the rate of suicide in the first 28 days after discharge from psychiatric hospital. METHODS Cohort study of patients discharged from psychiatric hospital. METHODS Scotland. METHODS All patients aged 15-84 who were discharged from Scottish psychiatric hospitals during 1968 to 1992. METHODS The rate of suicide (classified as codes E950-9 and E980-9 according to the International Classification of Diseases, Ninth Revision) within 28 days of discharge per 100,000 person years at risk for five year periods during 1968 to 1992. Crude, within cohort rates and externally standardised rates were calculated. RESULTS Overall, 196 male patients committed suicide in 20,520 person years at risk, and 171 female patients committed suicide in 24,114 person years at risk. A significant linear trend was seen in period effect on externally standardised mortality ratios in both sexes: a decrease in male patients (P = 0.008) and an increase in female patients (P = 0.0001). The adjusted standardised mortality ratio in 1988-92 compared with 1968-72 was 0.62 (95% confidence interval 0.39 to 0.98) in male patients and 2.73 (1.64 to 4.56) in female patients. CONCLUSIONS The increase in the rate of suicide in the 28 days after discharge in female psychiatric patients makes this an increasingly important period to target. The rise has occurred against the background of a reduction of 60% in the number of psychiatric beds for adults.