In patients with normal intraocular pressure (IOP), local ocular application of pilocarpine causes IOP elevation, reaching a maximum at 10–20 min, and a subsequent prolonged fall of IOP below the baseline. We have studied the effect of pilocarpine in normal subjects with low baseline IOP ( < 10 mm Hg). The initial rise was larger than in normotensive controls (21 vs. 12%) and the subsequent fall was of similar relative magnitude (20%) as that of normotensives. Lower baseline IOP values were associated with greater initial rises and smaller subsequent falls. The mechanisms that may explain the two phases of IOP response to the administration of pilocarpine are discussed.