A 15-year old Chinese boy was diagnosed to have Leber's hereditary optic neuropathy (LHOA), having manifested with typical findings of bilateral severe visual loss and telangiectasia at the optic disc. However, no family history was elicited and an interval of more than 5 years separated visual loss in the two eyes. The latter is an extremely uncommon finding. Visual improvement was rapid and marked after instituting intramuscular hydroxycobalamine 5 mg weekly. Bilateral improvement of Snellen acuity to 6/9 was achieved within 6 months. This is also unusual in that visual prognosis is generally poor in LHOA, although spontaneous remissions have occasionally been recorded. In addition, the eye with a longer history of poor vision responded to therapy first.