Timolol (TIM) and betaxolol (BET) were evaluated for their effects on both intraocular pressure and retinal sensitivity as determined from visual fields in a randomized two-year parallel study in 20 patients with primary open-angle glaucoma. All treatments were twice-daily in both eyes.TIM was more effective than BET as an ocular hypotensive agent throughout the two year period. With regard to retinal sensitivity as measured by automated visual fields, there was a decrease in retinal sensitivity in the first six months in the TIM and BET treatment groups by 0.5–0.6 dB, and 0.2–0.3 dB, respectively. However, at the one and two year visits, retinal sensitivity increased 0.8–0.9 dB in the BET treatment group only.It appears that ocular hypotensive efficacy may not relate to retinal sensitivity within a period of two years or less in patients with mildly to moderately elevated intraocular pressure. Further work may reveal the reliability of this observation, and its clinical relevance.