Fifty-three patients with Wilson's disease were studied with regard to ophthalmologic abnormalities. Of the 35 symptomatic patients initially seen and treated at the Mayo Clinic, 34 (97%) had Kayser-Fleischer rings and 6 (17%) had sunflower cataracts at the time of diagnosis. In patients followed for a year or more, penicillamine therapy resulted in improvement of the Kayser-Fleischer rings in 18 of 20 (90%) patients and total clearing of the sunflower cataracts in 4 of 5 patients. The specific pattern of copper deposition in Kayser-Fleischer rings and the improvement with treatment occurred along four reproducible stages. None of five asymptomatic siblings of patients with known Wilson's disease had Kayer-Fleischer rings at the time of initial study. In one (untreated) of the five, Kayser-Fleischer rings developed 20 months after the initial normal slit-lamp examination. The presence of Kayser-Fleischer rings, and the absence of other ophthalmologic signs (such as nystagmus, cranial nerve palsies, and other movement disorders), can be of great assistance in the diagnosis of Wilson's disease. Once the condition has been diagnosed, specific medical therapy with penicillamine and low-copper diet dramatically improves what would otherwise be an inevitably fatal course.