Conjunctival and Tenon's capsule biopsies from two patient groups were quantitatively analyzed by light microscopy. Group A consisted of 20 patients with a primary glaucoma for whom surgery was a planned primary treatment modality. Group B was comprised of 20 patients with a primary glaucoma who had received at least two types of antiglaucoma topical medication, for a minimum of 1 year (mean, 7.7 years) before surgery. All slides were examined by two masked observers. A significant increase in the number of macrophages, lymphocytes, mast cells, and fibroblasts in the conjunctiva and Tenon's capsule and a significant decrease in the number of epithelial goblet cells were seen in the group that received long-term drop therapy. These results suggest that exhaustive medical therapy, before surgery is offered, increases the number of tissue inflammatory cells. It is possible this may enhance the risk of external bleb scarring and filtration surgery failure.