A report is given of a black family with a dominantly inherited, neuro-retinal degeneration associated with abnormally large mitochondria, in which the cristae are disoriented. The disease is characterised by progressive external ophthalmoplegia, clear-cut macular degeneration, cerebellar dysarthria, spastic paraplegia and finally facial and bulbar weakness. A similar illness has been described in black families and individuals and we suggest that the disease may represent a specific syndrome, possibly confined to blacks, that lies within the spectrum of the so-called mitochondrionopathies.