Immunocytochemical methods were examined for their sensitivity in the detection of nuclear antigens (proliferating cell nuclear antigen, Ki-67 associated proliferative antigen and p53 protein) in the leukemic cells. A comparative study of the biotin streptavidin enhanced peroxidase technique, the biotin streptavidin enhanced alkaline phosphatase technique and the indirect immunoperoxidase technique showed that the indirect immunoperoxidase technique was more sensitive than the other techniques for detecting p53 protein. The results of several fixation methods demonstrated that formalin and methanol, formalin and ethanol (1:9) and buffered formalin acetone gave good results for detecting p53 protein. In the eosinophils and neutrophils the endogenous peroxidase reaction disappeared after microwave heating for over three minutes. Thus enzyme pre-blocking of blood smears could be omitted. Four solutions for microwave treatment were tested. Excellent antigen retrieval was obtained with pH6.4, pH7.4 phosphate buffer saline and pH6.0 citric acid. However, the nuclear antigens could not be retrieved and the positive reaction could not be obtained after the treatment with distilled water. The optimal microwave heating time was five to ten minutes. The indirect immunoperoxidase technique performed using microwave treatment under these optimal conditions may be potentially applicable for detecting low levels of nuclear antigens in the leukemic cells within conventional blood smears.