The matrix metalloproteinases (MMP) are a family of structurally related zinc-dependent extracellular matrix degrading proteinases that have been implicated in facilitating the migration and growth of pterygia. Both MMP- 3 and MMP-13 were found to be overexpressed in the fibroblasts at the head of pterygia and adjacent to denuded basement membrane, respectively. This laboratory study investigated the effects of Cyclosporine A (CsA) on the expression of MMP-3 and MMP-13 in cultured pterygium fibroblasts. Culture cells were obtained from the specimens taken at the time of pterygium or cataract surgery from the leading edge of pterygia and treated with various doses of CsA over different time periods. The results demonstrate that CsA induces inhibitory effects on migration of pterygium fibroblasts through the inhibition of MMP-3 and MMP-13 expression even at low doses and over short exposure period. This study gives insight into inhibitory CsA mechanism on pterygium fibroblast migration further warranting CsA clinical use for reducing the recurrence rates postoperatively and suggesting CsA as a possible agent to use in preventing pterygium progression.