Fibroblasts cultured from wound sites have been shown to have an altered phenotype compared to normal dermal fibroblasts and are generally regarded as target cells of the cytokine response at sites of injury. This study was undertaken to determine whether wound fibroblasts can contribute to proinflammatory cytokine production in wounds and, in particular, whether they are capable of secreting TNF. Wound fibroblasts were cultured from polyvinyl alcohol sponges implanted subcutaneously for 2 weeks in Balb/c mice. Fibroblasts harvested from the skin and subcutaneous tissue of untreated mice served as a control population of cells. All cells were passaged at least twice and then stimulated with a dose range of LPS. Supernatants were harvested 8 hr following stimulation and TNF was assayed using a standard L929 cell-killing assay. There was a significant TNF response to LPS by wound fibroblasts, evident as early as 4 hr following exposure to LPS and associated with an upregulation of TNF mRNA. Normal dermal fibroblasts did not secrete any measurable amounts of TNF in response to LPS. The results indicate that wound fibroblasts generate a brisk TNF response to stimulation with LPS, in contrast to normal subcutaneous fibroblasts. These data reveal an additional unique property of wound-harvested fibroblasts and suggest a possible contributing mechanism to disordered wound healing in the face of infection or conditions characterized by excessive fibrosis.