Exogenous polypeptide growth factors influence the rate of wound healing and other biological processes, but there is no direct evidence that these peptides have an intrinsic role. To test whether basic fibroblast growth factor is involved in wound repair, rats were implanted with subcutaneous polyvinyl alcohol sponges containing slow-release pellets releasing either a polyclonal neutralizing antiserum directed against basic fibroblast growth factor, preimmune IgG, or nothing. Histological and biochemical evaluation of the granulation tissue that infiltrated the sponges showed anti-basic fibroblast growth factor to cause significant reductions in DNA, protein, and collagen content when compared with either preimmune IgG or placebo at the early stages of wound repair.