Central areolar choroidal dystrophy (CACD) is a retinal disease which causes progressive profound loss of vision in patients during middle age. The disease is inherited as an autosomal dominant trait and shows genetic heterogeneity. Mutations in the peripherin-RDS gene on chromosome 6 have been reported in affected members of families transmitting the disease. A new locus at chromosome 17p13 was identified recently by a genome wide linkage search in members of a large Northern Irish family. We now report the refinement of the critical region for this gene to an interval of approximately 5 cM flanked by polymorphic markers D17S1810 and CHLC GATA7B03.