Isosorbide is an effective hyperosmotic agent which can be administered orally without gastrointestinal irritation. It is absorbed quantitatively and more than 95% of the administered dose is excreted unchanged in the urine. Oral administration of a 50% solution to rabbits or man results in prompt increases in osmolarity of the serum and profound decreases in intraocular pressure. The drug proves useful in acute primary and secondary glaucomas, and as preoperative medication for various surgical procedures including cataract extraction, retinal detachment, corneal transplant, and glaucoma operations.