Corneal thickness in the affected members of 3 families with Meesmann's epithelial dystrophy was statistically significantly less than that of the nonaffected members and of their controls. From our data one could speculate that the stroma rather than the epithelium is the primary source of the dystrophy. The thinner the cornea, the more marked the expression of the epitheliopathy. The affected members of the 2 families that were large enough for a separate analysis showed a marked difference in expressivity of the epithelial disorder. In one family the epitheliopathy showed a stationary character, while in the other there was a progression in the density of the epithelial vesicles.