Relaxin is involved in a variety of functions. Among them, relaxin influences gastrointestinal motility in mice mainly regulating the biosynthesis of nitric oxide, considered as the main substance causing smooth muscle relaxations. Relaxin is able to regulate the different nitric oxide synthase expression depending on the gut region considered. Relaxin also counteracts the hypermotility state, related to a defective nitric oxide production, observed in the gut of dystrophic (mdx) mice. From the above considerations, it appears that relaxin, in addition to its physiological roles, may be regarded as a therapeutic tool in gastrointestinal diseases characterized pathogenically by an altered nitric oxide production.