The participation of genetic factors in the origin of convulsive disorders is a controversial matter. In an attempt to study the influence of heredity in a selected group of patients, we evaluated 128 subjects that presented febrile febrile convulsions. Of these, 18 (14,3 % of the sample) had at least one relative affected by the same problem. Even though a more definite conclusion depends on sample enlargement and on setting up a control group, pedigree observation suggests the participation of an autosomal dominant gene, with incomplete and probably low penetrance, in the etiology of febrile convulsions.