Posterior polymorphous dystrophy (PPMD) is an autosomal dominant disorder of the cornea that is clinically recognized by the presence of vesicles on the endothelial surface of the cornea. The corneal endothelium is normally a single layer of cells that lose their mitotic potential after development is complete. In PPMD, the endothelium is often multi-layered and has several other characteristics of an epithelium including the presence of desmosomes, tonofilaments, and microvilli. These abnormal cells retain their ability to divide and extend onto the trabecular meshwork to cause glaucoma in up to 40% of cases. A large family with 21 members affected with PPMD was genotyped with short tandem repeat polymorphisms distributed across the autosomal genome. Linkage was established with markers on the long arm of chromosome 20. The highest observed LOD score was 5.54 (theta = 0) with marker D20S45. Analysis of recombination events in four affected individuals revealed that the disease gene lies within a 30cM interval between markers D20S98 and D20S108.