Objective To study the clinical, histological, and immuno‐histochemical findings of small cell carcinoma (SCC) of the urinary bladder, and also to delineate its behaviour in comparison with transitional cell carcinomas of the bladder.Materials and methods A retrospective review of 552 patients with bladder cancer yielded six cases (1%) of small cell carcinoma which were histologically identical to pulmonary small cell anaplastic carcinoma. Clinical data and follow‐up were collected. Aside from the conventional histological parameters, an immunohistochemical study with AE1–AE3 and Cam 5.2 keratins, epithelial membrane antigen, neuron‐specific enolase, chromogranin, synaptophysin, ACTH, calcitonin, and prostatic specific antigen was performed.Results The clinical presentation did not differ from conventional transitional cell carcinoma, haematuria being the most frequent complaint (four cases). All the cases presented as flat tumours. On light microscopy, there were oat cell (four cases), intermediate (one case) and mixed oat‐cellJintermediate (one case) variants. Three cases were associated with transitional cell carcinoma. Dysplastic changes were observed in the adjacent urothelium in one case only. At the time of diagnosis, all tumours were deeply invasive (pT3). Three cases were Stage III and three Stage IV, with involvement of regional lymph nodes and metastases to the liver (two cases) and lung (one case). Immunohistochemically, epithelial markers were variably expressed as AE1‐AE3 keratin (5J6), Cam 5.2 keratin (2/6) and epithelial membrane antigen (3/6). Neuron specific enolase was demonstrated in every case. Chromogranin, however, was expressed in only one case. Synaptophysin, ACTH, calcitonin, and prostatic specific antigen all gave negative results. All the patients died of the disease and the overall length of survival was very poor (range 5–2 5 months, mean 13.3).Conclusion Small cell carcinomas show the same histological patterns as their pulmonary counterpart. Immunohistochemistry reveals a wide spectrum of activity, enolase and keratins being the most constant. The present study confirms that the overall prognosis of this tumour