Urinary stone disease and bladder cancer are two of the most commonly seen urologic diseases in Taiwan. Tumor necrosis factor-alpha (TNF-alpha) is one of the cytokines secreted by macrophages and is related to a sequence of events in response to inflammation and cancer formation. We investigated the polymorphism of the TNF-alpha gene promoter -308 as a genetic marker in searching for the association between these two commonly seen urologic diseases. One hundred and fourteen patients with transitional cell carcinoma of the urinary bladder and 103 patients with calcium oxalate stone were compared with 150 healthy controls. The polymorphism was detected by polymerase chain reaction-based restriction analysis (Nco I endonuclease). The results revealed no significant differences between normal individuals and the patients with the two commonly seen urologic diseases (P > 0.05). We concluded that the polymorphism of the TNF-alpha promoter -308 is not a valid genetic marker for these two urologic diseases.