Du Pont De Nemours perfected a new enzyme immunoassay for the screening of anti-HIV 1 antibodies, characterized by its rapidity: 2 hours of incubation, when the normal procedure needed 3 hours 30 minutes of incubation. We tested with the normal procedure and the shortened one 4,025 randomly selected blood donors. 55 samples of the SNTS panel and 10 sera representing the Western-Blot reference panel of the "Retrovirus" study group of the SNTS. We can say that shortening the incubation time results in certain advantages opposite the previous procedure: time saving (1 hour 30 minutes); improved specificity: the rate of false positive, 0.37% with the normal method, drops to 0.07% with the short one; good sensitivity, since all the individual positive samples were detected but it seems slightly less sensitive than the normal method for the diluted positive samples.