The clinical response of 57 adult patients with Cushing's syndrome due to bilateral adrenocortical hyperplasia or adrenocortical adenoma is documented following resolution of hypercortisolaemia by various forms of treatment. Despite satisfactory biochemical remission of the disease the clinical result was far less satisfactory when assessed by persistence of obesity (55%), menstrual irregularity (41%), hypertension (29%) and insulin-dependent diabetes (22%). Myopathy, hirsuitism and psychological abnormalities persisted to a lesser extent. The mortality rate of the series over a 30 year follow-up period was 4 times that of a general population matched for sex, age and year of entry into the series. Cardiovascular disease was the cause of death in 85%. Irreparable cardiovascular disease is produced early in the course of hypercortisolaemia, emphasizing the vital importance of the earliest possible recognition and treatment of this disease.