The fluorescence method was compared with the Fite-Faraco method for detecting acid-fast microorganisms in paraffin sections of cases of leprosy. Biopsies were obtained from 50 cases of leprosy covering all varieties and at varying stages of treatment. The fluorescence method was better than the Fite-Faraco method; 22 biopsies showing acid-fast organisms in fluorescence microscopy and 20 in the Fite-Faraco method. Its superiority was evidenced in two cases in which the organisms were very scanty. Fluorescence microscopy can also be used to determine the Bacterial Index and the Morphologic Index of organisms. The Morphologic Index, however, was one and a half times higher than that obtained by the Fite-Faraco technic. The ease and speed of fluorescence microscopy appear to be a great advantage.