Purpose. To examine whether transforming growth factor-β2 (TGF-β2) induces the expression ofα-smooth muscle actin (SMA), a biochemical marker of myofibroblasts, in cultured bovine retinal pigment epithelial (RPE) cells.Methods. Bovine RPE cells were cultured in F-12 nutrient mixture supplemented with 5% fetal bovine serum (FBS), with or without TGF-β2 (0.01–10 ng/ml) for 6 days. During this culture period, cells did not reach a confluence. Alpha-SMA was detected immunocytochemically with a mouse monoclonal antibody, and the ratio of the number ofα-SMA positive cells to the total number of cells was calculated.Results. About 10% of the cells in control cultures with only FBS were positive forα-SMA. TGF-β2 increased the ratio of positive cells dose-dependently (p<0.0001), while a neutralizing antibody against TGF-β2 blocked this effect.Conclusions. TGF-β2 induced expression ofα-SMA in bovine RPE cells.