A vaccine against hepatitis B surface antigen (Institut Pasteur Production) was assessed in 138 haemodialysis patients in a placebo-controlled randomised double-blind trial. In an interim analysis, hepatitis B infections were observed in 21% of the vaccine group and 45% of the placebo group (p less than 0.02). 2 of the infections in the vaccine group and 12 of the infections in the placebo group occurred after the third injection. 60% of the vaccine recipients had an immune response. 4 months after the first injection the mean titre of anti-HBs was 120 mlU/ml.