Does the opening pressure of hydrostatic shunts influence the clinical outcome for patients suffering from idiopathic normal-pressure hydrocephalus (iNPH)? Between September 1997 and January 2003, 122 patients with iNPH were surgically treated by implanting a hydrostatic shunt at the Departments of Neurosurgery of the Unfallkrankenhaus Berlin and the University of Homburg/Saar. The results of the clinical examination, the intrathecal infusion test, and the cerebrospinal fluid tap test served as decision aids regarding shunt implantation. As part of a prospective randomized study, all patients were examined before surgery, after surgery, and 1 year after the intervention. Forty-three percent of the patients had a very good outcome, 25% had a good outcome, 20% had a fair outcome, and 12% had a poor outcome 1 year after shunt implantation. Patients treated with an opening pressure rating of 50 mm H2O in the low-pressure stage of the gravitational valve showed a statistically significant better outcome than those with an opening pressure rating of 100 or 130 mm H2O. Of the valve-independent complications observed after the intervention (11% shunt-related complications), 8 (7%) were dislocations of ventricular or abdominal catheters, 3 (2%) were catheter tear-offs, and 3 (2%) were shunt infections. Of the valve-related complications (10%), 4 patients (3%) suffered underdrainage, 8 patients (7%) showed radiologic signs of overdrainage, and 4 patients (3%) showed symptomatic overdrainage. According to present knowledge, hydrostatic shunts with an opening pressure of 50 mm H2O for the low-pressure stage are the optimal therapy option for patients with iNPH. Because of the prompt switching function as soon as the patient changes his or her posture (eg, lying down, standing, sitting), the Miethke Gravity Assisted valve (Aesculap) is more suitable for such cases than the Miethke DualSwitch valve (Aesculap). Can programmable gravitational valves contribute to further optimization of the outcome while minimizing the valve-related complications?