Tissue repair and wound healing are complex processes that involve inflammation, granulation, and remodeling of the tissue. In this study, we evaluated the in vivo effects of curcumin (difeurloylmethane), a natural product obtained from the rhizomes of Curcuma longa on wound healing in rats and guinea pigs. We observed faster wound closure of punch wounds in curcumin-treated animals in comparison with untreated controls. Biopsies of the wound showed reepithelialization of the epidermis and increased migration of various cells including myofibroblasts, fibroblasts, and macrophages in the wound bed. Multiple areas within the dermis showed extensive neovascularization, and Masson's Trichrome staining showed greater collagen deposition in curcumin-treated wounds. Immunohistochemical localization of transforming growth factor-beta1 showed an increase in curcumin-treated wounds as compared with untreated wounds. In situ hybridization and polymerase chain reaction analysis also showed an increase in the mRNA transcripts of transforming growth factor-beta1 and fibronectin in curcumin-treated wounds. Because transforming growth factor-beta1 is known to enhance wound healing, it may be possible that transforming growth factor-beta1 plays an important role in the enhancement of wound healing by curcumin.