A total of 19 patients receiving topically administered echothiophate iodide for control of chronic open angle glaucoma were treated with orally administered pralidoxime chloride (Protopam) to determine which small doses would reverse cholinesterase levels. One group of ten patients received 4.5 gm of pralidoxime chloride in divided doses weekly for four weeks. A second group of nine patients received 10.5 gm in divided doses weekly for three weeks. No significant changes in intraocular tension or facility of outflow were noted after pralidoxime chloride therapy, but a significant rise in erythrocyte cholinesterase activity (0.07 delta pH units; P < 0.01) was demonstrated. No significant toxic signs were noted. Clinical ramifications are discussed.