PURPOSE: To report the characteristic findings of a macular pattern dystrophy in patients with diabetes and deafness resulting from the mitochondrial point mutation at position 3243 and to expand the clinical spectrum of this condition by describing functional testing results. METHODS: Four diabetic patients who were referred to the eye department for diabetic fundus examination were found to harbor a macular pattern dystrophy. Further examination of visual fields; color contrast sensitivity; and the ear, nose, and throat; and molecular analysis of the mitochondrial genome were performed. Two of our patients were sisters. Their relatives also were examined. RESULTS: All four patients were found to harbor the mitochondrial point mutation at position 3243 and presented clinically with the phenotype of diabetes and deafness. The macular pattern dystrophy described in these patients seems to be typical for this condition. Results of a 9-year follow-up study of one of the patients showed mild progression of atrophic changes. The overall prognosis of the retinopathy is likely to be good. CONCLUSION: These cases demonstrate the need for further molecular investigations when a macular pattern dystrophy is found in a patient with diabetes and deafness.