Clinical reexamination and DNA linkage analysis were carried out in an X-linked progressive cone dystrophy (XLPCD) family, previously described by Pinckers and Timmerman in 1981. In a large pedigree segregating XLPCD, by use of > or = 27 markers spanning the entire X chromosome, a novel locus for XLPCD was identified in Xq27. All other regions on the chromosome could be excluded. Since this novel locus is distinct from previously identified genes or regions involved in XLPCD, we further establish genetic heterogeneity underlying this disease entity.