The hypotensive efficacies of timolol, vistagan, and betoptic were studied in three groups of patients with primary open-angle glaucoma, matched for the clinical diagnosis, somatic condition, and number of patients. The hypotensive activity of timolol was found superior to that of vistagan or betoptic, but its administration was associated with tachiphylaxia, that is an essential disadvantage of the drug. The advantage of vistagan and betoptic is the possibility of their administration to cardiopulmonary patients with contraindications against timolol therapy.