Bladder cancer manifests many different forms, ranging from superficial to aggressive muscle invasion, which suggests that various genetic alterations are responsible. Several attempts have been made to establish correlations between specific genetic alterations and various grades of the disease. Numerous types of chromosomal abnormalities have been observed, involving [1p, 1q, 2q, 3p, 4p, 5q, i(5p), +7, +8, 8p, 9p, 9q, 10q23-25, 11p, 11q, +11, 13q, 14q, 17p, 18q, 21q, and Y]. In addition, p53 mutations and loss of heterozygosity on various chromosomes have recently begun to shed light on the molecular pathways of transitional cell carcinomas of the bladder. We have begun to focus on specific genomic sites (especially 9q), although the heterogeneity of the disease and the variable presentation suggests divergent progression pathways. When the genetic basis of bladder cancer is fully understood, new diagnostic and therapeutic strategies will be developed, which in turn may promote better clinical management by pathologists and urologists.