The western blot analysis of 170 patients with HIV-1-infection demonstrated that 47% of the patients in latent stage, 58% of the patients with lymphadenopathy-syndrome and only 25% of the patients with the full-blown picture of AIDS showed the complete pattern of HIV-specific antibody response. This antibody response is mainly directed against the env-encoded envelope proteins gp160, gp120 and gp41, against the gag-encoded core proteins p55, p24 and p17 as well as against the pol-encoded enzymatic proteins p66, p51 and p31. Antibodies against gp160 and gp120 were present in nearly all patients, whereas the prevalence of the other antibodies decreased with the stage of the disease. Statistical significant differences were found particularly between patients with LAS or AIDS respectively. Antibodies against p17 were detected in 74% of the patients with LAS but only in 25% of the patients with AIDS. The lack of antibodies against p17, p24 or p51 was significantly associated with lower mean CD4/CD8-ratios (p less than 0.007) and higher mean serum levels of IgA (p less than 0.001) and beta-2-microglobulin (p less than 0.001). One third of the patients with LAS and this reduced pattern of antibody response developed AIDS within six months. These results demonstrate that the detection of antibodies against p17, p24 or p51 is of prognostic importance. A serological profile which lacks the antibody response against at least two of those three viral antigens indicates a progression of the disease activity.