Rapid discrimination of acute myelogenous and non-myelogenous leukemias is of great importance when chemotherapy is urgently needed in severely ill patients. For decades the most reliable cytochemical method for this classification is the demonstration of myeloperoxidase in blast cells [1-4, 6, 7]. We combined the simplified myeloperoxidase stain as described by Kaplow with a brief stain similar to Pappenheim's procedure or with commercially available Hemacolor rapid blood smear: this proved to be a simple staining method that permits good morphological judgment of the cells as well as reliable demonstration of peroxidase activity. This procedure takes less than 10 min using Hemacolor and can easily be done with prepared solutions without technical assistance.