The success of glaucoma filtration surgery depends mainly on an incomplete wound healing process in the area of the fistula. Since Kornblueth and Tenenbaum's investigations in 1956 it has been known that aqueous humour has intrinsic antiproliferative properties. It is assumed that ascorbic acid is involved in the regulation of the wound healing process after filtration surgery. To evaluate the antiproliferative effect of ascorbic acid in vitro, we used cultured fibroblasts of bovine Tenon's capsule and bovine sclera. Incubation of these cells with ascorbic acid at concentrations ranging from 0.5 to 3 mM/L led to dose-dependent inhibition of cell proliferation. The half-maximal inhibitory concentration was 1.0 mM/L for both cell types. Physiological concentrations of ascorbic acid may be valuable in the pharmacological prevention of failure of glaucoma filtration surgery. However, extensive clinical investigations are needed to clarify whether topical intraoperative or postoperative as well as oral administration of ascorbic acid inhibits fibroblast proliferation after glaucoma filtration surgery.