We wished to find what pressure changes were caused in Codman-Medos programmable valve by magnetic exposure and filliping. This pressure-adjustable valve system was used in an experimental investigation of the changes measured in the pressure setting following MR exposure and other impulses. In one experiment, two valves were affixed to a human model: one was installed in the right retroauricular region and the other at the anterior chest wall. The pressure was changed in 58 (80.6%) of 72 tests in the valve in the right retroauricular region and in 46 (63.9%) of 72 tests in the valve at the anterior chest wall. In some tests with the valve pressure originally set at 200 mmH2O striking changes to lower pressures were observed. In the other experiment, the changes of pressure settings in seven patients with a shunt system installed were checked before and after random filliping with the tip of an index finger 50 times. In all 7 patients, the pressures initially set were greatly changed, by up to 120 mmH2O of the maximum range. These results demonstrate that the pressure setting of the shunt system can be changed by various shocks, including magnetic impulses, and that the pressure level of the shunt system must be constantly monitored.