The skin lesions from 16 leprosy patients were studied by immunofluorescence technique using monoclonal antibodies against monocytes (OKM1 and Anti-Mo) and la-like antigen. Acid phosphatase activity was evaluated using naphthol AS-BI phosphate as substrate. The macrophages seem to be a heterogeneous population in concern with the antigens here studied as well as the enzimatic activity. Ia-like antigen was expressed in a great number of cells throughout the clinical spectrum.