Pindolol, a strong beta-adrenergic blocking agent, instilled into the conjunctival sac of normal and glaucomatous eyes, produced a significant drop in intraocular pressure. This was not, at first, accompanied by any variation in outflow facility; only after prolonged treatment did an increase in facility appear, which accounted only for one-third of the tension-lowering effect. The drug was well tolerated, and did not affect either pupil motility or corneal sensitivity. It seems suitable for a trial use in the treatment of glaucoma.