In this paper it is done the genetic study of a large family that segregates the hereditary optical atrophy gene The modality of the hereditary transmission is the sex-linked recessive form (Leber's form). Five generations were studied, with a total of 134 individuals. Thirteen are affected (12 men: 1 woman). The study of the heredogram allows the observation of the high occurrence of women carriers and that affected men with descendents (2 married men in the heredogram) exhibit normal offspring (22 individuals, being 16 men and 6 women). One affected woman carrier is also observed. Such observations are in accordance with the literature. This study allows one to conclude by the high importance of genetic counselling, considering that the normal women carriers, which occur in great number, segregate the gene to individuals who will manifest the atrophy.