We used aqueous humor from cataract patients and glaucoma patients as a medium for tissue culture of subconjunctival fibroblasts. The aqueous humor from cataract patients consistently inhibited the growth of their own subconjunctival fibroblasts, whereas that of some of the glaucoma patients did not. We found a significant correlation between the success of the filtering operation and the ability of that patient's aqueous humor to inhibit the growth of fibroblasts in tissue culture.