Urothelial carcinomas arising from the upper urinary tract (renal pelvis and ureter) are rare and few molecular genetic studies of these tumors have been conducted to date. We investigated hyperploidy at chromosomes 3, 7, and 17 using a multitarget fluorescence in situ hybridization system to identify genetic alterations in patients with urothelial carcinomas of the upper urinary tract. Chromosomal aberrations are seen most frequently in the high-grade tumors. A highly significant relationship was found between an increase in the percentage of hyperdiploidy and high grade for each chromosome (chromosome 3, P = 6 × 10(-4); chromosome 7, P = 2 × 10(-4); chromosome 17, P = 6 × 10(-5)). To determine whether these associations were independent for each chromosome, the correlation between percentage of hyperdiploidy for each pair of chromosomes was examined. In each case, the correlation was highly significant (R = 0.89-0.91). No statistically significant association was found between percentage of hyperdiploidy and tumor stage for any chromosome.