Adult kidneys have limited regenerative capacity following a prominent acute kidney injury. As understanding regenerative mechanisms is the key to discovering therapeutic strategies for preventing and treating renal diseases, in recent years, researchers have hotly debated whether progenitor/stem cells offer a support system for renal repair. The Romagnani-led group identified CD133 stem cells in the parietal epithelium and renal tubules, and their data indicate that these progenitor/stem cells support renal repair in the glomeruli and renal tubules. The Humphreys and Bonventre group used the lineage-tracing technique. They observed no contribution of progenitor cells to tubular repair, but they later reported that the differentiated tubular cells responsible for tubular repair actually gained some characteristics of progenitor cells. This review article will focus on major updates regarding the controversial progenitor/stem cells in renal regeneration and highlight some new progenitor cell issues in renal mass lesions.