A neuro-ophthalmological examination was performed on 47 asymptomatic offspring in the female line and 13 offspring in the male line in families with Leber's hereditary optic neuropathy. Fourteen (61%) of the 23 asymptomatic males and nine (38%) of the 24 asymptomatic females in the female line had telangiectatic microangiopathy of the peripapillary arterioles and capillaries. Increased tortuosity of capillaries, medium-sized arterioles, and venules were also seen in the fundi of several asymptomatic family members. The 13 offsprings in the male line did not have microangiopathy. Nerve fiber abnormalities were not seen in asymptomatic persons. The photographically verified findings are described, classified, and discussed. It is suspected that Leber's disease is primarily a microvascular disorder. The vascular abnormalities detected in the asymptomatic family members probably indicate increased risk of Leber's disease developing. During the prospective follow-up of three years, three asymptomatic boys with microangiopathy have experienced Leber's disease.