Between May 1982 until January 1997 we investigated 200 patients suspected for normal pressure hydrocephalus (NPH) by performing an intrathecal infusion test. According to our experiences gait ataxia is the leading symptom of NPH. Regarding dementia we could not find a significant difference compared to cerebral atrophy. Bladder incontinence can be characterised as a symptom of late-stage NPH. The complete Hakim trias should not be overestimated in differential diagnostic considerations. Graduation of NPH and cerebral atrophy after the results of the infusion test in an early and late stage enables prognostic evaluation of the course of disease. Patients with NPH in an early stage report in the follow-up on an improvement of their symptoms after shunt operation (65 percent of patients), whereas 50 percent of the patients with late stage NPH were improved. The computer-aided infusion test allows secure differentiation between patients with NPH and those with cerebral atrophy.