All patients with primary open-angle or primary angle-closure glaucoma requiring trabeculectomy between January 1982 and January 1983 were entered into a randomized prospective study to evaluate the effect of postoperative corticosteroids. Twenty-three eyes in Group 1 received a cycloplegic and topical antibiotic. Twenty-nine eyes in Group 2 received the same treatment, with the addition of topical 1% prednisolone acetate. Twenty-three eyes in Group 3 received the same treatment as Group 2, with the addition of systemic prednisone. Success rate was significantly improved with the use of topical corticosteroids. Systemic steroids did not prove to be of any added benefit over topical use alone.