- The prevalence of HIV antibodies in 44 heterosexual female partners and 56 nonsexual family household contacts of 61 HIV seropositive haemophiliacs (41 adults and 20 children or adolescents) was determined to evaluate the risk of transmission of HIV infection. HIV antibodies were determined by enzyme-linked immunosorbent assay and positive reactions were confirmed by Western blotting. HIV antibodies were demonstrated in 4/40 (10%) regular heterosexual partners of 40 seropositive patients with haemophilia A. Four temporary heterosexual partners of one additional seropositive haemophiliac were seronegative. 56 nonsexual household contacts including 30 parents, 13 siblings and 13 children of 29 seropositive haemophiliacs were all negative for HIV antibodies. Thus transmission of HIV occurred from seropositive haemophiliacs to their heterosexual partners but not to nonsexual household contacts.