Bladder cancer represents the fourth most common malignancy among men and the eighth most common in women in the Western world. Of patients with bladder cancer 70% to 80% initially present with non–muscle invasive bladder cancer (NMIBC) (stages Ta, T1 or carcinoma in situ). Primary therapy for NMIBC is transurethral resection of the tumor (TUR-B). About 30% to 85% of patients have recurrences after TUR-B. Hence, in stage Ta–T1 bladder cancer, one immediate intravesical instillation of chemotherapy after TUR-B should be performed to reduce or prevent the recurrences in all patients. Further treatment depends on the patient's risk group. An immediate instillation can be considered sufficient for patients with low-risk tumors. For patients with intermediate- or high-risk tumors, additional adjuvant installations are needed. The timing of one immediate intravesical instillation is crucial. But, an instillation within 6 h after TUR-B seems to be most effective. There is no single drug that is superior with regards to efficacy.