These data comprise 1,231,024 routine tests carried out over a 5-year period on voluntary blood donors. The percentage of positive results on the machines varies from 1 to 3% of the total number of samples tested. Antibodies identified either by manual or automated techniques make up 15-20% of the positive screening reactions. Rhesus, Lewis and P systems prevail, whilst Duffy, Kidd and Lutheran systems are absent. This screening has three main advantages: the supply of plasma for our production of test sera, or therapeutic immunoglobulins; protection of the recipient; partial information on the donor’s immunohaematological state, especially for the risk of giving him incompatible blood sometimes in the future.