In order to set the nozzle opening pressure for an injection nozzle, in particular for a diesel injection nozzle, to an accuracy of around 1%, the method provides that the injection needle is first pressed against the valve seat with a closing force (Fz), and then when two different test pressures (pU, p1, p2) are applied to the injection nozzle the test forces (Fz, F1, F2) effective on the injector needle are measured, with the pressure stage (A) being determined from the measured test forces and the test pressures applied, and finally using the pressure stage (A) a nozzle valve with a suitable valve spring force (Fv) is selected to correspond to the desired nozzle opening pressure (pD).