Keratoconus, a bilateral corneal disease, is characterized by modifications in corneal shape and thinning of the stroma. From a biochemical point of view, a decrease in collagen content, probably due to the high collagenase activity, has been reported. Gamma Interferon (gamma-IFN), Tumor Necrosis Factor (TNF), and Interleukin 1 (IL1) are peptide regulatory factors involved in immunological responses, but they also play a role in the synthesis of collagen and prostaglandin E2 by fibroblasts. In these experiments, we have determined the number of membrane binding sites for gamma-IFN, TNF, and IL1, and the dissociation constant (Kd) for each radiolabelled ligand. All experiments were carried out on cultured corneal stromal cells. Data from normal human corneas and from keratoconus were compared. No differences were found concerning gamma-IFN and TNF binding sites between normal corneas and keratoconus, while fibroblasts from keratoconus proved to bear four fold more IL1 binding sites than normal fibroblasts, with similar Kd.