Intravesical chemotherapy has been shown to reduce or prevent recurrence of low-grade, low-stage transitional cell tumors of the bladder. Thiotepa, mitomycin C, doxorubicin, and bacillus Calmette-Guérin (BCG) are the drugs most widely used for intravesical chemotherapy in the United States; only thiotepa has FDA approval for use within the bladder. Results of studies with these agents are reviewed. Prospective, randomized studies are needed to determine the ability of the agents to prevent progression of high-grade tumors to muscle invasion.