Purpose To determine the incidence of alloimmunization against red cell antigens and the thermal amplitude and specifi city of antibodies in multitransfused patients and multiparous women.Methods Antibody screening was performed in 30 nontransfused orthopedic surgery cases (control), 504 multitransfused patients and 325 multiparous women. Antibody screening at 4°C, 22°C and 37°C was carried out in a saline phase, by indirect antiglobulin technique (IAT), using papain cystein, low ionic strength solution (LISS) and polyethylene glycol (PEG). ResultsIn multitransfused patients IgM antibodies were more frequently detected at 4°C and the IgG antibody incidence was 7.1% by enzyme method, 7.7% IAT, 9.4% LISS, 10.2% using PEG & 10.2% multiparous women. Bad obstetric history cases had signifi cantly higher incidence of alloimmunization. The antibody specifi city of antibodies was mainly in Lewis, Rh, Kidd and MN systems.Conclusion Antibody screening before transfusion, at set time intervals after transfusion and during antenatal period is recommended.