The human granulocytes were isolated. Using hybridoma techniques, a hybridoma cell line (HSN) producing monoclonal antibody (McAb) against human granulocyte was obtained. The antibody belonged to IgG1 subclass. It was confirmed by immunohistochemical tests that HSN reacted selectively not only with human granulocytes, but also with their bone marrow precursors. Whereas human lymphocytes and red blood cells retained negative in the tests. No cross-reaction was observed with the peripheral blood cells in other animals. Its affinity constant was 5.7×10,8,L/mol, and the number of epitopes per granulocyte was 4.7×10,5,. Monoclonal antibody displayed no loss of immunoreactivity after labelled with ,99m,Tc.