Hermansky-Pudlak syndrome (HPS) is an autosomal recessive disorder characterized by the triad of tyrosinase-positive oculocutaneous albinism, bleeding diathesis due to storage-pool deficiency of platelets, and a lysosomal ceroid storage disease. The disorder is particularly frequent in Puerto Rico and in an isolated village in the Swiss Alps. We have used a linkage disequilibrium mapping approach to localize the HPS gene in both of these groups to a 0.6 centiMorgan interval in chromosome segment 10q23.1-q23.3. These results indicate that the Puerto Rican and Swiss forms of HPS are either allelic or that they result from mutations in very closely linked genes in this region. This region of distal chromosome 10q is syntenic to the region of mouse chromosome 19 that includes 'pale ear' (ep) and 'ruby-eye' (ru), which must be considered as potential murine homologues to human HPS.