The fungus Microcyclus ulei is the causative agent of leaf blight in rubber trees, which is one of the most important diseases affecting this crop, since it causes intense defoliation. Several races of this pathogen have been described in Brazil based on a series of diverse differential clones. According to the reactions of 11 differential clones already reported in the literature (MDF 180, Fx 3844, Fx 985, Fx 4098, Fx 2261, Fx 2804, Fx 3899, IAN 6158, IAN 3087, IAN 717 and PA 31), containing the species Hevea brasiliensis, Hevea benthamiana and Hevea pauciflora, a cluster analysis of the binary data referring to virulence of this disease was performed by using the Jaccard method. The cluster analysis was fitted according to the centroid method. Results indicated the existence of 53 different races of this pathogen in Brazil.