Contractile and phenotypic properties of human fibroblasts from healing wounds were compared to those of dermal fibroblasts using in vitro models. Wound fibroblasts were recovered from implants, made of a polyvinyl alcohol sponge threaded into a perforated silicone tube, 12 days after their subcutaneous implantation in human volunteers. Dermal fibroblasts were isolated from the skin of healthy subjects. Two morphologically different fibroblast populations were observed in cells cultured from implants. In order to characterize these fibroblast populations, intracellular α-actin expression was studied by immunofluorescence labeling of cells cultured in monolayer. This protein was detected in less than 1% of the dermal fibroblasts. By contrast, 30 to 40% of wound fibroblasts were labeled and contained fiber networks of α-actin. These results confirm the presence of myofibroblasts in human wound healing tissues. The contractile property of fibroblasts and myofibroblasts was evaluated using a three-dimensional cell culture model (fibroblast populated collagen gels). Cells were incorporated in a collagen matrix and cultured for 14 days. The surface area of collagen gels was measured every day. Our results show that wound fibroblasts strongly contract collagen gels during the first 24 hr (surface area at 24 hr = 20-55% of initial surface area) in comparison to dermal fibroblasts (surface area at 24 hr = 70-75% of initial surface area). This superior level of contraction was observed until the fifth day of culture. In conclusion, these results show that in human granulation tissue, the myofibroblast phenotype is abundant at Day 12 postwounding and that granulating wound fibroblasts have greater contractile capacity than dermal fibroblasts, in vitro. These gathered observations suggest that myofibroblasts are responsible for wound contraction in vivo.