Forty patients who had normal-pressure hydrocephalus were examined neuropsychologically before and 12 months after a ventriculoatrial shunt operation. Comparison of the preoperative and postoperative test results showed that cognitive functions improved in 16 patients, were unchanged in 19, and deteriorated in 5. Moreover, we found that the outcome of the operation depended on patient selection criteria. When three or more of the following preoperative signs were present (known cause, short history, low cerebrospinal fluid outflow, small sulci and/or periventricular hypodensity indicated by computed tomography), an improvement in cognitive function was seen in 80% of the patients after a shunt operation.