['To characterize the Fas-Fas ligand system, a main apoptotic pathway, in transitional cell carcinoma (TCC) of the urinary bladder, by analysing the expression of Fas and Fas ligand (FasL) in TCC samples.', 'Archival paraffin-embedded tissues from 37 patients with TCC were analysed by immunohistochemistry to determine Fas and FasL expression.', 'Fas and FasL were detected on the cell surface and cytoplasm of respectively 34 (92%) and all cases analysed. The expression of Fas and FasL did not differ with the cytological grade of TCC.'] Does transitional cell carcinoma express high levels of Fas ligand in vivo?