The results of a third seroprevalence survey of antibody to HIV in U.K. haemophiliacs, done in 1987, are presented. Out of 3028 men with haemophilia A living in the U.K. during the period 1980-1987 who had been tested for HIV antibody, 39% were positive, and out of 517 men tested with haemophilia B, 5% were positive. For both haemophilia types the proportion of seropositive men is greater among patients with a severe coagulation defect. No new seroconversions are known to have taken place after November 1986.