Instillation of 2 drops of 4% solution of atenolol decreases the ocular pressure in open angle glaucoma. 2. In 12 glaucomatous patients treated as in-patients, 4 daily instillations of 4% solution lower the average tension of the group below 20-22 mm Hg day and night. 3. The tensionnal effects of 4 or 6 daily instillations on out-patients seems to be less effective. 4. The hypotensive effects of atenolol, on some of the patients at least, decreases during the second month of uninterrupted treatment. However, the response to a single dose remains constant even after a long term treatment. 5. Treatment with atenolol is remarkably well tolerated. It does not provoke either local or general side effect. 6. Although the combination of atenolol and myotics or carbonic anhydrase inhibitors produces an additive pressure lowering effect this results in a loss of the advantages of atenolol with regard to absence of undesirable pharmacological effects.