Arginine supplementation has been identified as advantageous in experimental wound healing. However, the mechanisms underlying this beneficial effect in tissue repair remain unresolved. Animal studies suggest that the beneficial role of arginine supplementation is mediated, at least in part through NO. The latter component mediates processes involved in tissue repair, including angiogenesis, epithelialization and collagen formation. This prospective study is performed to investigate arginine metabolism in acute surgical wounds in man. Expression of enzymes, known to be involved in arginine metabolism were studied in donorsites of skin grafts of 10 hospitalized patients undergoing skin transplantation. Plasma and wound fluid levels of arginine metabolites (ornithine, citrulline, nitrate and nitrite=NOx) were measured using High Performance Liquid Chromatography. Expression of iNOS, eNOS, arginase-1 and arginase-2 were studied by immunohistochemistry in paraffin sections of skin tissue. Arginase-1 concentration was measured in plasma and wound fluid using ELISA. Arginase-2 was determined using Western Blot analysis. We observed increased levels of citrulline, ornithine, NOx and arginase-1 in wound fluid when compared with plasma. Arginase-2 was expressed in both plasma and wound fluid and seemed higher in plasma. iNOS was expressed by neutrophils, macrophages, fibroblasts, keratinocytes and endothelial cells upon wounding, whereas eNOS reactivity was observed in endothelial cells and fibroblasts. Arginase-1 was expressed in neutrophils post-wounding, while arginase-2 staining was observed in endothelial cells, keratinocytes, fibroblasts, macrophages and neutrophils. For the first time, human data support previous animal studies suggesting arginine metabolism for an NO- as well as arginase-mediated reparation of injured skin.