The purpose of pretransfusion compatibility testing is to prevent immune mediated hemolytic transfusion reactions. Our study aimed to evaluate the gel test for detection of clinically significant antibodies in repeatedly transfused patients. We investigated 200 thalassemic patients in whom, blood group, Rh-D, Rh phenotype determination, antibody screening and identification were done using an ID Microtyping System. Red cell alloantibodies were detected in 21 patients (10.5%). Among these patients, Anti-E was detected in 5 (23.8%), anti-D in 4 (19%), anti-K in 4 (19%), anti-e in 3 (14.3%) and each of anti-Fy(a), anti-Js(a), anti-Lu(a), anti-N and anti-s in one patient (4.8%). Anti-E showed the highest frequency in the 21 positive cases that developed clinically significant antibodies. The study revealed statistically significant correlation between development of transfusion reactions, frequency of blood transfusion and the duration of blood transfusion with the incidence of development of clinically significant alloantibodies. It is concluded that the gel test is an easy, quick and reliable method for detecting clinically significant antibodies. Antibody screening and identification is recommended prior to transfusion to detect if there is blood group incompatibility other than the ABO and Rh.