This paper describes an automated apparatus combining Rosenfield's and Lalezari's antibody screening and identification basic technics. PVP bromelin and low ionic strength acid polybren channels are used; agglutinates are decanded; the remaining cells are hemolyzed and the optical density is then measured through a colorimeter and recorded on a chart; speed is of 40 samples an hour. This machine was also used for irregular antibody screening and identification. Sensitivity is shown to be equal to that of manual technics for ABO, Lewis, Lutheran as well as K, S, M, Kpb, Xga, U and Vel antibodies detection. Nevertheless, a much greater sensitivity is achieved (titers 3 to 10 times higher) than by manual technics for Rh, -k, S, Fya antibodies detection. Polybren channel is suitable for anti-Rh, Duffy, I and M (human detection; bromelin channel however, has a greater sensitivity for other specificities. Anti-M and anti-N sera from rabbits were shown to be non specific when using this machine. Over almost 15 000 sera tested, no antibody (detected by manual techniques) escaped the automated screening. This antibody detection machine was applied to compatibility tests prior to transfusion. (21 480 units were tested. aimed to be transfused to 5 611 patients). A third, PVP without bromelin, was set in parallel in order not to let escape any anti-M, even a weak one. The sera distributor was slaved to the cells distributor so that the whole procedure was automated. Furthermore, each serum was tested against red cells to be transfused, but also against the patient's own red cells to be transfused, but also against the patient's own red cells and against two selected red cells panels, so as to ensure irregular antibody detection at the same time. Using this machine, 3 to 4% of the cell samples were rejected, i.e. more than with usual techniques. All manually detected antibodies were identified, but also some others, which showed only weak reactions by classical techniques. Total results can be obtained within 20 to 30 minutes, which is quite rapid, compared to techniques using for example antiglobulin tests.