• The glucocorticosteroid sensitivity of patients with primary open angle glucoma and normal patients was determined by the quantity of dexamethasone required to reduce concanavalin A-induced lymphocyte blast transformation to 50% of control values (I50 ). This was performed under culturing conditions employing both serum-free medium and medium supplemented with 10% autologous serum. A comparison of the I50 between normal subjects and those with primary open angle glaucoma did not show a significant difference in steroid sensitivity under either of the two culturing conditions. It is concluded that persons with primary open angle glaucoma do not have a generalized inherited or acquired cellular hypersensitivity to glucocorticoids.