Bladder cancer corresponds to a tumor type whose clinical behavior is difficult to predict. A better understanding of this pathology is expected from molecular genetics, which brings together cytogenetics and molecular biology. Therefore, we have tried to overview correlations between chromosome abnormalities and the presence, in the vicinity of the altered loci, of genes (oncogenes and others) that could be involved in bladder oncogenesis and/or tumor progression. In addition to oncogene activation by point mutations, gene amplification, or deregulation of gene expression, several cytogenetic as well as molecular evidences point to genetic deletions (existence of "tumor suppressor genes") being involved in those processes.