PURPOSE OF REVIEW: Relaxin is a peptide hormone named for its ability to soften the birth canal in preparation for parturition. Not surprisingly, therefore, subsequent attention has focused on its role in remodeling connective tissue in other organs, especially in circumstances of pathological fibrosis and scarring. This review discusses the renoprotective and therapeutic potential of relaxin in the kidney, which has highlighted its relevance in human pathophysiology. RECENT FINDINGS: Growing evidence suggests that the kidney is both a therapeutic target and potential source of relaxin. Although the expression of renal relaxin is low, endogenous relaxin appears to play an important role in connective tissue homeostasis within the kidney, whereas exogenous relaxin has been shown to consistently and rapidly abrogate renal fibrosis at many levels, primarily through an ability to interfere with the actions of transforming growth factor beta-1. Furthermore, the vasodilatory and angiogenic properties of relaxin, in addition to its ability to improve renal function in humans, have contributed to its therapeutic significance in renal disease. SUMMARY: Accumulating evidence from studies at the preclinical and clinical level has demonstrated a potential antifibrotic and regenerative capacity of relaxin, directly relevant to the kidney.