A new serological test, the gelatin particle agglutination (PA) test, was developed for the detection of antibody to human immunodeficiency virus (HIV). The sensitivity of the PA test was the same as that of enzyme-linked immunosorbent assay (ELISA) among 761 US and Japanese sera tested. However, false-positive cases were found in 1.2% of all sera in ELISA but in 0% in the PA test (P less than 0.05). There was 100% agreement of seropositivity between PA and a confirmatory indirect immunofluorescence (IF) test. In addition, the agglutination test was reproducible. Thus, the test should be useful for the mass screening of anti-HIV antibody in blood donors.