Thirty-seven patients with thalassemia major (TM) were studied to determine the extent and rate of endocrine complications. Mean haemoglobin and ferritin concentrations were 8.8 +/- 0.6 and 3597 +/- 1931, respectively. Provocation tests for growth hormone secretion were applied in patients with standing heights below the third centile and/or growth velocities below the 10th centile. Sexual maturation was assessed by using the criteria of Tanner. Glucose metabolism was assessed by fasting plasma glucose and glucose tolerance test. Basal thyroid function was measured and thyrotropin-releasing hormone tolerance test was carried out. Growth retardation was found in 40 per cent of patients and growth hormone deficiency was a prominent cause of growth retardation. Gonadal dysfunction was detected in 47 per cent of patients. Hypothyroidism was observed in 16 per cent and impaired glucose metabolism in 10.8 per cent patients. The high rate of endocrine disturbances indicates the importance of regular follow-up of thalassemia major patients with regard to endocrine complications of the disease.