Muon spin rotation/relaxation (μSR) are sensitive methods to measure internal magnetic field distributions and their dynamics in solids. At the Paul Scherrer Institute (PSI) in Villigen, Switzerland a μSR spectrometer is available which allows μSR experiments at pressures up to 0. 9 GPa. The temperature range is 350 K to 10 K and a typical sample size is 7×60 mm. This paper describes high pressure μSR studies. Measurements on ferromagnetic Gadolinium (Gd) will be presented as an example. In ferromagnetic Gd the direction of easy magnetization is temperature dependent (spin turning). We found a significant influence of applied pressure on the temperature dependence of the spin turning process.