Antibodies to specific HIV viral antigens were measured by ELISA recombinant proteins representing gag and env amino acid sequences of human immunodeficiency virus (HIV) (E. I. du Pont de Nemours, Wilmington, DE) and by a Western blot system using biotinavidin detection (Biotech Research Labs, Rockville, MD) on 36 HIV antibody-positive hemophiliacs (HTLV-III ELISA, du Pont) on whom date of seroconversion was known and on whom serial samples where available between 1977 and 1986, representing 2-8 years following seroconversion. The 36 included 9 acquired immunodeficiency syndrome (AIDS) and 27 non-AIDS (7 AIDS-related complex (ARC); 4 other HIV class IV, 16 asymptomatic) patients. The development of AIDS was preceded 1-4 years by loss or lack of antibody to gag (p15, 24, or 55) and/or to pol (p31, 53, or 64), each p less than 0.001, compared with non-AIDS patients. Correlation between Western blot and recombinant assays was good except in one Western blot p24 (gag) only seroconverter who showed strong reactivity to env by recombinant assay. In conclusion, HIV antibody patterns appear to show prognostic significance in HIV-infected hemophiliacs.