Extra-hepatic obstruction of the portal vein is a well known cause of hypertension in childhood and 55 out of the 97 patients (57 per cent) seen with this condition presented before they were 15 years old. However, nearly half our cases (43 per cent) presented in adult life. Haematemesis was the commonest mode of presentation in both the adult and childhood group although splenomegaly was common, especially in the children. The severity and frequency of haematemesis increased during puberty in the children. Twelve children and three adults have now not bled for between five and 30 years, 10 of them ceasing spontaneously and five following surgery. Intra-abdominal infection or septicaemia precipitated the portal venous obstruction in 38 patients (39 per cent), though the exact cause of such obstruction in patients who had no cirrhosis was obscure in about half the cases. Ascites was present in 18/51 (35 per cent) of the children and 24/35 (69 per cent) of the adults. Its presence was associated with an increased mortality (p less than 0.01). Nineteen out of 42 (45 per cent) patients with ascites also had portal-systemic encephalopathy. Twenty-four patients died, nine having presented during childhood, variceal haemorrhage was responsible for death in 19 and infection in five. Sixty-four patients underwent 114 operations for variceal haemorrhage. Mortality was greater in the surgical group compared with those managed conservatively. Surgery is therefore indicated only in the rare case where bleeding cannot be controlled by medical means.