Irregular antibody anti erythrocyte antigen is one of the causes of transfusion complications. Patients of hematological disorders who have been blood transfused could be more at risk of irregular antibodies. The study on 764 patients of hematological disorder at Bach Mai hospital, the authors obtained some results as follows: Percentage of patients with irregular antibody is 7.86 percent, the common antibody specificity is system MNSs, Rh, Lewis, and the P. The hight rate of irregular antibodie present at the patients more blood transfused and at the female patients who had more than 3 times of pregnant, but also even in patients not having received a blood transfusion any time.