Rabbit corneal endothelial primary cultures and subcultures with initial high seeding densities (split ratio 1 : 2) and low seeding densities (split ratio 1 : 4) were maintained routinely in Falcon Petri dishes. Ascorbate, 75 microgram/ml, was added daily to experimental cultures to evaluate its effect on growth of endothelial cells. With supplemental ascorbic acid, the cells grew at a slow rate, had a shorter lifespan, and reached a lower cell density at confluency than did control cells. The inhibitory effect of ascorbic acid on cell growth was more pronounced with cultures plated at low cell densities and with cells in later passages. Cultures grown with ascorbate contained a greater number of elongated cells and large-sized cells with vacuoles. A basal lamina was observed even in control cultures with no supplemental ascorbate.