The effects of transforming growth factor-β(TGFβ) and epidermal growth factor (EGF) on the synthesis of collagen and fibronectin, and on the proliferation of human corneal stromal fibroblastsin vitro, were evaluated. Human corneal stromal fibroblasts in culture were incubated for 48 hours with TGFβor EGF in the absence of serum. Collagen and fibronectin in the culture media were measured by a collagenase-digestion assay and a competitive ELISA, respectively. The effects of the growth factors on proliferation were assessed by3H-thymidine incorporation. Collagen synthesis was dose-dependently stimulated by TGFβ; at a concentration of 1 ng/ml of TGFβ, a 120% increase in collagen synthesis was seen over that of controls (p<0.01). EGF, at a concentration of 10 nglml, induced a 40% increase in collagen synthesis over that of controls (p<0.01). The maximum stimulation by TGFβwas greater than that by EGF (p<0.05). Fibronectin synthesis was stimulated by TGFβand EGF in a dose-dependent manner; 230% (p<0.001) and 210% (p<0.01) increases in fibronectin synthesis were caused by 10 ng/ml TGFβand EGF, respectively. TGFβand EGF dose-dependently stimulated3H-thymidine incorporation. The maximum increases in3H-thymidine incorporation reached 180% (p<0.001) and 190% (p<0.001) over that in controls, at 10 ng/ml concentrations of TGFβand EGF, respectively. In conclusion, both TGFβand EGF are potent stimulants of collagen and fibronectin synthesis and proliferation. Therefore, these two growth factors may be effective alternatives or additional choices for the treatment of corneal ulcer.