The urologic oncology community recognizes the importance of bladder cancer as a significant public health problem. As the fourth most common malignancy diagnosed in U.S. men and the ninth most common in women, bladder cancer is a highly prevalent cancer with an estimated 5-year prevalence of 490,000 patients in the U.S. (2001) and over 1,000,000 worldwide (2004). Bladder cancer is the most expensive cancer to diagnose and treat. Important clinical questions abound and there are a growing number of both NIH and industry funded clinical trials attempting to answer these questions. The EORTC has played a critical role in conducting phase II and large phase III randomized trials addressing critical questions in the management of non-muscle invasive and invasive bladder cancer. The present article reviews this important area of clinical trials research.