64 families containing a proband with corneal endothelial dystrophy were examined in order to study the hereditary nature of the disease. Data concerning the frequency of occurrence, severity of the disease, ratio of affected females to males, relationship of the disease with age, and other factors were the subject of a previous report. 7 pedigrees which reflect features of endothelial dystrophy within the 64 families are presented. These features include multiple females in a family being affected, multiple consecutively affected generations, the occurrence of offspring with disease more severe than the parent, and endothelial decompensation (edema) at a relatively young age (less than 40 years of age). The importance of examining family members whenever possible rather than relying on history alone is emphasized. A statistical analysis of the inheritance pattern was performed. Endothelial dystrophy does not seem to follow a strict autosomal dominant pattern even though superficial inspection suggests autosomal dominant inheritance (both males and females affected, successive generations affected, 38% of relatives over the age of 40 years affected). Even though we were unable to determine a specific genetic mode of inheritance in these 64 families with endothelial dystrophy, we do feel that endothelial dystrophy is at least in part an inherited disease. Future investigations might prove sex-linked dominance, genetic heterogeneity, the influence of environmental factors, or a multifactorial etiology.