Antibody to Human Immunodeficiency Virus (HIV) was detected by an enzyme immunoassay (Genetic Systems LAV EIA) in low risk populations from five geographically distinct sites. The assay used virus (LAV) grown in the T-cell line CEM. In blood and plasma donor populations, 0.4 percent of the samples were initially reactive and 0.2 percent were repeatably reactive. Fourteen of the twenty-one (67 percent) repeatably reactive specimens were confirmed by immuneprecipitation (RIP). The assay demonstrated 99.9 percent specificity compared to RIP and had a positive predictive value of 67 percent. The data suggest that this test generates a low proportion of false positive EIA results and is highly suitable to screen blood donors.