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Bladder cancers are classified as: transitional cell carcinoma (TCC), the most frequent in Europe/USA, squamous cell carcinoma (SCC), more frequent in the Middle East and in Africa, adenocarcinoma and small cell carcinoma, rare. TCC exhibit pseudo diploid karyotypes with only a few anomalies in early stages, evolving towards pseudo-tetraploides complexes karyotypes. Partial or complete monosomy 9 (-9) is an early event, found in half cases. Deletion (11p) or -11 is found in 20-50% of cases, more often in high grade and invasive tumours. Del(13q) is found in 25% of cases and correlated with high grade/stage; tumours with Rb alterations are invasives. Del(17p) is a late event, found in 40% of cases; P53 alterations are correlated with grade and stage, tumour progression, and a worse prognosis. Del(1p), i(5q), +7, and many other rearrangements - more often deletions than duplications - are frequently found. These losses of heterozygocity point to a multistep complex process involving tumor suppressor genes. In SCC, monosomy 9 is also an early event, even more frequent than in TCC; homozygous deletion of P16 is frequent. Trisomy 7 seems to be more frequent than in TCC. Chromosome 17 is often implicated, especially in high grades/stages; the profile of mutations of P53 is different from what is found in TCC. Allelic losses of 3p, 8p, 9p, 9q, 17p are frequent. The karyotype is more complex in advanced grades/stages, as in TCC.