Editor,—We report a case of late onset of Leber’s hereditary optic neuropathy (LHON) in a 59 year old patient with HIV infection being treated long term since 1991 with zidovudine. The onset and course of the patient’s eye disease as well as the diagnostic process were analysed. Molecular genetic testing revealed the mitochondrial DNA (mtDNA) mutation in nucleotide position 11778 confirming the diagnosis of LHON. In our patient late disease expression may be interpreted as a result of the rare combination of the 11778 mutation with HIV infection and long term zidovudine treatment. This is the first report on a patient with LHON suffering from additional HIV infection.