Lymphadenectomy at the time of cystectomy for muscle invasive bladder cancer offers, at worst, staging and prognostic information, and, at best, improved survival or cure. This article assesses both the evidence to support performing a lymphadenectomy at the time of cystectomy and the extent of lymphadenectomy that should be performed. The minimum lymph node dissection that should be performed at the time of cystectomy for muscle invasive bladder cancer should include meticulous removal of all tissue in the internal iliac, external iliac, and obturator areas, extending to include the distal common iliac nodes and nodes medial to the internal iliac vessels. Whether more extensive dissections than this improve survival is not yet clear.