The safety profile of the different glaucoma medications is an important issue when initiating therapy in glaucomatous patients. The decision on which medication to prescribe depends not only on the type of glaucoma, but also on the patient's medical history and needs a detailed knowledge of the potential side-effects of each medication. Medications side effects may be an important cause of non adherence for the individual patient The properties of the drugs, the composition of the glaucoma eyedrops and the dynamics of ocular drug absorption must be considered. The ocular surface changes induced by long-term antiglaucomatous treatment especially by their preservatives are a major cause of intolerance or poor tolerance to glaucoma eyedrops. Moreover topically applied ophthalmic medications can attain sufficient serum levels through absorption into conjunctival and nasal mucosas to have systemic effects and to potentially interact with other drugs. Then this presentation will deal with the ocular and systemic side-effects which can be encountered with the different classes of the currently available glaucoma topical medications. Recommendations than can be applied to reduce both frequency and severity of side-effects of glaucoma medications will be stressed on. Concurrently patients should be fully informed not only about their disease but also the medications they used and what side-effects they have to expect.