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A new, simple method for direct count of blood monocytes, was developed using alphanaphthyl butyrate and hexazonium pararosaniline. This method enables us easily to differentiate monocytes specifically stained red-brown from other white blood cells in the same manner of enumeration of WBC. The average of absolute monocyte count in 40 healthy volunteers was 245±91/cmm, slightly less than the number indirectly calculated from May-Giemsa stained smears and slightly greater than the number from peroxidase stained smears. In general, this new method seemed to be as reliable as the indirect method differentiating 1,000 leukocytes or more in blood smears. Thus, the method described in this paper can be used in ordinary laboratories and is also applicable to identification and enumeration of macrophages.