Background. We examined the effects of interferon- (IFN-) on protein production of extracellular matrix (ECM) components in cultured human subconjunctival fibroblasts or those stimulated by exogenous transforming growth factor 1 (TGF1). IFN- reportedly up-regulates Smad7, an inhibitory mediator of TGF-Smad signaling, and blocks TGF effects. Methods. Proliferation and migration as well as the ultrastructure of these cells were examined in the presence and absence of IFN-. Cell migration was examined using an in vitro wound healing model in monolayer fibroblast cultures. Results. The results showed that IFN- reduced ECM production in normal subconjunctival fibroblasts, as well as in those treated with TGF1, below the control levels. IFN- had no effect on cell proliferation and fibroblast ultrastructure. On the other hand, IFN- delayed defect closure in monolayer cell sheets in a dose-dependent manner. Immunohistochemistry also revealed that the addition of IFN- attenuated the translocation of Smads2/4 into the nuclei of TGF1-treated subconjunctival fibroblasts. Conclusion. These findings suggest that IFN- may be clinically effective in attenuating excessive ECM accumulation in conjunctiva after ocular surgery and in the presence of inflammatory ocular surface disorder. IFN- modulates the Smads2/4 pathway of TGF1 signal transduction toward the up-regulation of ECM components.