Twelve patients with chronic simple glaucoma were treated for 1 week with Ocusert-40, and the effects on the pupil, intraocular pressure, and refraction were measured. A comparison was made with the effects of pilocarpine eyedrop therapy in 8 of these patients. Both forms of pilocarpine treatment gave satisfactory control of intraocular pressure and both constricted the pupil to a similar degree shortly after initiation of treatment. During the week on Ocusert-40 the pupils redilated, so that 54% of the initial miosis remained after 7 days' wear. There was, however, considerable variability in the pupillary sensitivity to Ocusert-40 within and between eyes, and it is suggested that this may have been partly due to variable release rates of pilocarpine. Only minor decreases in visual acuity and refraction resulted from pilocarpine in either form. Seven of the 12 patients rejected Ocusert-40 because of discomfort or inability to retain the device.