Two patients aged 17 and 25 years with Kearns syndrome are described. This condition is characterized by the triad of chronic progressive external ophthalmoplegia, pigmentary degeneration of of the retina and cardiac conduction defects. A review of the literature reveals frequent association with other symptoms, mainly cerebellar ataxia, neurosensory hearing loss, small stature, muscle weakness, mental retardation or dementia and endocrine disturbances. In skeletal and extraocular muscle biopsies, abnormalities of mitochondria, at present of unknown significance, have been found. CSF protein is almost always increased. The etiology of this multisystem disorder remains obscure. The 58 published cases have been sporadic, with no evidence of hereditary transmission. The prognosis seems mainly to depend on the progressive cardiac conduction defects, since several patients have already died in the second or third decade due to heart block. Patients with progressive external ophthalmoplegia should be investigated for Kearns syndrome. If appropriate, implantation of a cardiac pacemaker should be considered.