We compared perioperative conjunctival biopsy specimens from 31 consecutive trabeculectomy patients to determine if there were any histologic differences between black and white glaucoma patients. We found a statistically significantly greater mean and distribution of mast cells and neutrophils in the white patients. No significant difference was found in the mean number of goblet cells, eosinophiles, macrophages, fibroblasts, plasma cells, or lymphocytes; or in thickness of the epithelium, vascular density, or collagen or mucopolysaccharide staining. We conclude that histological conjunctival factors that could be evaluated preoperatively probably are not related to the poor results in black patients of filtration surgery noted by some investigators.