The sympathetic system is composed of alpha and beta receptors. Beta blockers block the beta effect competitively. They slow the heart and decrease its contractile strength. They block bronchodilatation and the vasodillation of muscular arteries. Timolol is a non specific beta blocker. It decreases intraocular pressure by reducing aqueous humor formation. It does not change outflow facility. Its action starts twenty minutes after a topical drop, is maximum two to four hours later and lasts 24 hours and more. Timolol o.50% seems equivalent to pilocarpine 4% while Timolol 0.25% seems equivalent to epinephrine 2%. There is a further drop in pressure when added to pilocarpine, diamox as maximum medical treatment. Tables show its advantages, drawback, adverse reactions, and precautions to be taken.