A fifteen-year study was made in the neurologic clinic of the school of medicine, of the City of Sao Paulo; 466 patients were examined clinically and with EMG determination of enzymes, biopsies and genetic counsel. The diagnosis varied much and some important findings at heart level, with overload, were discovered in some cases. In the cases in which the diagnosis was not confirmed; CPK was determined, which was increased in all cases, but was not so with GOT, GPT and LDH. A family pattern was found in the Duchenne Becker distrophy, limb-girdle syndrome, fascioscapulohumeral and oculopharyngeal. The biopsy exposed 15 of the 18 polymyositis cases. Genetic counsel was given to heterozygotes with PMD genes of great risk of presentation. An acute stage, detected by CPK dosage, was foreseen for adolescent heterozygotes.