Primary cultures of corneal epithelial cells from adult albino rabbits were exposed briefly to various concentrations of NaOH and formaldehyde. The release of plasminogen activator from the cells was stimulated or inhibited during a 6-day recovery period. This differential effect was dependent on the chemical concentration and duration of cell recovery. The modulation of plasminogen activator release in thein vitrosystem would be useful for predicting ocular toxicity of substances.