Of 109 patients with cirrhosis and endoscopically demonstrated oesophageal varices who had not bled, 56 were treated by sclerotherapy and 53 were treated conservatively. Patients were assigned to one of three categories according to varix size and Child's classification of severity of liver disease. Severity of liver disease increased with varix size. Frequency of haemorrhage in the control group also increased with varix size: haemorrhage occurred from small varices in 35% of patients, from medium varices in 53%, and from large varices in 83%. Prophylactic sclerotherapy diminished the frequency of variceal bleeding and overall mortality: over 25 months, frequency of bleeding was 9% in the therapy group and 57% in the controls, with mortality rates of 23% and 55%, respectively.