A retrospective analysis of the discharges over a five-year period from the Public Health Service Indian Hospital in Fort Defiance, Ariz, confirmed the clinical impression that diabetes mellitus is a fairly common but extremely mild disorder among the Navajo Indians. Of 105 diabetic patients, only three had a history of ketonuria, and seven had retinopathy. The juvenile form of diabetes is unknown and not one case of ketoacidotic coma was observed. Thus abnormal glucose tolerance appears to be a relatively isolated, benign chemical abnormality in the Navajo.