Optic atrophy and typical visual field defect were found in two brothers some months following a rapid decrease in visual acuity. The optic disc was hyperemic and edematous, furthermore microangiopathy, hemorrhages, and papilloedema were present in the ocular fundus of the third brother some days after an acute loss of central vision. In the present study the pathogenic and differential diagnostic significance of the acute phase of Leber's optic neuropathy is discussed. Considering the fundus changes in the acute phase and the course of the disease, the authors tend to reject the idea of a hereditary systemic disease of the nervous system. The hereditary factors should be searched neither in the nerve tissue nor in the ectodermal system.