As we are looking for non-intrusive flow velocity measurement, we can quote such methods as Laser Doppler Anemometry (LDA) and Particle Image Velocimetry (PIV). In-cylinder application on engine involves facing difficulties which come from the tridimensional pulsed turbulent flow, confined and large spatial measurement, short characteristic timing… Our work deals with the development and the application of PIV to determine the two dimensional instantaneous velocity vectors of in-cylinder flow during the admission event upright the inlet ports of a two stroke engine. We describe the different steps and the many precautions necessary for a valid measurement: apparatus choice, image processing, engine adaptation. The first results of this application on a two stroke engine in static position (piston at Bottom Dead Center, BDC) and in motored conditions are presented. A second approach is to demonstrate for a static case the possibility of measuring the mean velocity over a large plane despite the low resolution of a CCD camera.