A comparative study comprising 30 patients with glaucoma and 11 ocular hypertensives showed that pilocarpine 2%-4% and metoprolol 3% lowered the intraocular pressure to the same extent over a 4-week period. The magnitude of effect corresponded to 29.0% of the untreated pressure level in the pilocarpine group and to 31.9% in the metoprolol group. No statistically significant difference in the pressure lowering effect was found between glaucoma and ocular hypertension. Sufficient control of the intraocular pressure could not be achieved in approximately 35% of the patients with metoprolol single therapy and a tendency towards fading efficiency of metoprolol was noted, but no significant tachyphylaxis appeared during a 5-month follow-up period. Local irritation was the predominant side-effect of metoprolol treatment. Objective adverse reactions recorded were transient, epithelial keratopathy (3 patients) and exanthema (1 patient). Deterioration of a pre-existing visual field defect was observed in one case.