From a series of 15 consecutive patients with a normal-pressure hydrocephalus examined over 2 years. 10 showed frank improvement with oral acetazolamide. The drug was a first-choice treatment in 5 cases and was given up after a spinal tap in 5 cases. Clinical response occurred even in the most severe cases, although it was slightly less impressive for intellectual impairment than for gait or bladder disturbances. Tolerance was excellent with a daily dose of 250 to 500 mg. The benefit remained stable on a more than 1 year follow-up in 8 cases. We suggest that acetazolamide should be tried in patients with normal pressure hydrocephalus prior to considering shunting.