Transurethral resection of bladder tumors (TURBT) is the standard of care for the diagnostics and primary treatment of bladder tumors. These are removed by fragmentation using loop diathermy. The resection area is coagulated for hemostasis. An important aspect is always a complete resection with an adequate amount of detrusor muscle in the specimen. Postoperative intravesical instillation of single-shot chemotherapy has been proven to reduce recurrence rates. Methods for improved tumor visualization (particularly photodynamic diagnostics) are used to enhance tumor detection rates particularly in multifocal tumors or carcinoma in situ (CIS). Thus, recurrence and progression rates can be reduced. Depending on the histological examination of the TURBT specimen, follow-up treatment for non-muscle invasive bladder tumors are adjuvant instillation treatment using chemotherapy or Bacillus Calmette-Guérin (BCG), second look TURBT and early cystectomy or for muscle invasive bladder tumors, radical cystectomy or (oncologically subordinate) trimodal treatment with renewed TURBT, radiotherapy and chemotherapy are indicated. Possible complications of TURBT include bleeding with bladder tamponade, extraperitoneal or intraperitoneal bladder perforation and infections of the urogenital tract.