Multiple transfusion over a long period of time lead to alloimmunization in a certain percentage of cases. In such cases it becomes difficult to find proper units of blood which will be compatible with the patients. In advanced countries rare blood units are stored in a frozen state and are utilized when such a situation arises. In our country, however there is no direct method to find out the specificity of antibodies. The indirect methods which are applied in such cases, are discussed.