The theoretical part of this paper presents the mechanism of the IOP lowering effect using these drugs, the indications of treatment and the main side effects. The second part consist of the experimental study made on rabbits, using the izopropilic ester of (+)Cloprostenol as an hypotensive agent. We have registered the IOP values and the main side effect--conjunctival hyperemia. The third part consist of the clinical study, made on a test lot of 23 patients. We have used the same substance and in the experimental study, as a unique treatment or in association with a beta-blocker or a pilocarpine derivative. The following-up has implied: the IOP, the ophthalmoscopic appearance of the optic disc, the visual field, the visual acuity and the main side effects. In the end, we have formulated the conclusions of these studies.