Invasive urinary bladder carcinomas are characterized by a high number of cytogenetic alterations which are thought to pinpoint the location of critical genes, some of which may be involved in cell cycle control. To identify genomic alterations that may affect such genes the proliferative activity (Ki67 labeling index) was assessed in 93 invasively growing bladder carcinomas analyzed by comparative genomic hybridization. Only a few changes were significantly associated with rapid tumor cell proliferation, including 3p+ (p=0.0357), 6p+ (p=0.003), 8q+ (p=0.0273), and 11q- (p=0.0329). Among these alterations 6p+ is of particular interest because high level 6p22 amplifications occur frequently in bladder cancer. The particular strong association between 6p+ and a high tumor cell proliferation being independent of grade and stage suggests that a putative oncogene on 6p22 involved in cell cycle regulation.