OBJECTIVE To evaluate the protein expression of fibroblast growth factor receptor-3 (FGFR3), hamartin, 14-3-3sigma, Aurora-A, and E-cadherin using immunohistochemistry (IHC) in a series of human bladder carcinomas and to evaluate their value in distinguishing T1a from T1b tumours and in predicting their behaviour, as T1 urothelial bladder tumours present great diagnostic and therapeutic challenges to pathologists and clinicians. PATIENTS, MATERIALS AND METHODS Tissue microarrays were constructed from 94 patients (Ta 20, T1a 31, T1b 14, and T2 29 patients) using tissue obtained at first disease presentation. RESULTS FGFR3 and 14-3-3sigma were the only markers that were significantly associated with tumour grade and 14-3-3sigma was significantly associated with tumour stage. Furthermore, none of these markers could help in distinguishing T1a from T1b tumours. After adjusting for the E-cadherin expression, FGFR3 expression was a significant factor in predicting the time to recurrence in T1a/T1b. Furthermore, among all the clinical variables, grade and depth of invasion were the only ones that had a significant value in predicting T1a/T1b tumour progression. CONCLUSIONS Even though the staging of T1 to T1a/T1b is not a common practice and it is not included in the Tumour-Node-Metastasis classification, our data clearly confirmed the importance of a proper sub-staging of T1 tumours whenever feasible.