Trisomy of chromosome 17 is associated with the development of papillary renal cell tumors (RCT). We have analyzed 37 papillary RCT by applying 25 polymorphic microsatellite markers and found an overlapping duplication including loci D17S1795 and D17S1306 on chromosome 17q21. This region was then analyzed in additional 118 sporadic and hereditary papillary RCT. Overlapping partial duplications at the chromosome 17q21.32 region localized the papillary RCT gene to an approximately 300 kb genomic sequences flanked by loci D17S787 and D17S1799. Altogether, 92% of the 100 papillary RCT showed allelic duplication at this region. We did not find mutation in coding sequences or altered expression of the hepatic leukemia factor gene, which is mapped the smallest duplicated interval, in any type of RCT. Therefore, another gene within the 300 kb region might be responsible for the development of papillary RCT.