Twenty-five (4.8%) of 520 hemodialysis patients were seropositive for antibody to human T-cell lymphotropic virus type III/lymphadenopathy-associated virus (HTLV-III/LAV) by enzyme immunoassay. Four had high reactivity on enzyme immunoassay and positive results of Western blot tests, and one of the four had a positive culture. The remaining 21 seropositive patients had low reactivity on enzyme immunoassay, negative results of Western blot tests, and negative cultures. All had received blood transfusions and 19 had antibodies to antigens associated with the H9 cell line used to propagate HTLV-III for serological tests. We found that HTLV-III/LAV was not transmitted in the dialysis centers. Frequent blood transfusion places dialysis patients at risk for HTLV-III/LAV infection, but may more commonly lead to false-positive results of enzyme immunoassay tests.