Transitional cell carcinoma (TCC) provides a unique model of cancer recurrence and progression. Sequential tumours (n=100) from 57 patients with an index pTa or pT1 TCC were studied using fluorescence in situ hybridisation (FISH), to determine aberrations of chromosomes 1 and 8. Thirty-seven patients experienced recurrences; eleven developed muscle invasive tumours (pT2+). Polysomy of chromosomes 1 or 8 was associated with pT1 TCC (P=0.0017 and P=0.0037, respectively), but not with recurrence. Progression was associated with polysomy of chromosomes 1 (P=0.003) and 8 (P=0.011) in pTa/pT1 recurrences, but not with stage. In conclusion, patients who subsequently developed invasive TCC (pT2+) had significantly higher rates of aneusomy (90%) in their superficial cancers than those patients who did not progress (P=0.009). Investigation of sequential tumours in patients with recurrent and progressive TCC showed that polysomy of chromosomes 1 and 8 were linked to subsequent detrusor muscle invasion, but not recurrence per se.