Growth factors have the ability to stimulate matrix synthesis and cellproliferation in rabbit flexor tendon. Maximal stimulation effects of growthfactors have a wide variation. It depends upon the different anatomic sites ofthe tendon segment, the kinds of growth factor, the concentration of growthfactors, and the time sequence. Since proliferation was an early component ofintrinsic tendon healing, we investigated the short-term dose response to fourdifferent growth factors on in vitro rabbit's tendon culture. We evaluated theeffects according to the various concentrations of recombinant humaninsulin-like growth factor 1 (IGF), recombinant human epidermal growth factor(EGF), fibroblast growth factor (FGF), and recombinant human platelet-derivedgrowth factor-BB (PDGF). Fetal calf serum was the most potent stimulator of cellproliferation and protein synthesis in in vitro rabbit's tendon culture. Matrixsynthesis and cell proliferation were stimulated dose-dependently by IGF betweenthe doses of 50 and 150 ng/ml. The maximum mitogenic effect of EGF was observedat the concentration of 100 ng/ml (1.3 times more than the media-only controlculture). The rabbit's tendon responded significantly dose-dependently to PDGF,whereas there was no significant response to FGF.