Background: This study intends to determine the frequency and clinicopatholog- ical characteristics of different types of bladder tumors, particularly transitional cell carcinoma in cystoscopic bladder biopsies and resections in the local patient population and compare these findings with local and international reports.Methods: The study was conducted in the Department of Histopathology, Sindh Institute of Urology and Transplantation, Karachi, Pakistan from December 1996 to December 2001. All patients with bladder growth who presented to the Urology Clinic of Sindh Institute of Urology and Transplantation (SIUT) during the study period and in whom a cystoscopy and bladder biopsy were performed, were included in this study. The clinical and demographic data and the pathological diagnoses were retrieved from the original surgical biopsy reports.Results: Out of 500 patients, there were 421 (84.2%) males and 79 (15.8%) females. The mean age was 57.5±8.6 years (range: 4 to 82 years). Among the primary bladder tumors, transitional cell carcinomas were the most common (94.3%) malignancy. A majority of these cases (62%) presented with superficial disease, whereas in 38% the disease was muscle-invasive at initial diagnosis. Grading was possible in all except two cases, which contained only necrotic tumor tissue. A vast preponderance of tumors (74.5%) were well-differentiated, while 25.5% were poorly-differentiated.Conclusion: This study demonstrates that the vast preponderance of bladder tumors is of urothelial origin and malignant. Benign tumors are very rare. The clini- copathological characteristics and frequency distribution of different types of bladder tumors in the local population are, in general, comparable to those reported in the world literature.