In order to evaluate the risk of HIV transmission during conception or pregnancy from seropositive male haemophiliacs to their children, we have investigated the families of 8 HIV antibody positive haemophilia A patients. HIV antibodies could be demonstrated in 1/9 mothers after delivery of her second child, whereas all the other mothers tested were seronegative. Of the 14 children studied at least 7 must have been conceived when the father was already seropositive. HIV antibodies were tested for in 6 of these 7 children; all were negative. All 14 children are healthy and free from clinical signs of HIV infection. We conclude that the overall risk of perinatal HIV transmission in haemophilic families should be low and this knowledge may be invaluable in family counselling.