Details of air flow in a direct injection diesel engine was investigated with a steady flow test rig. A laser doppler velocimeter was used to characterize the three dimensional air flow generated by two kinds of inlet ports. In order to obtain the distribution of flow velocity in a cylinder section, interpolation was carried out. A stereographic display of the three dimensional velocity vectors in the cylinder space allowed easy comprehension of the flow chracteristics. Angular momentum flux and turbulence kinetic energy in the region closer to the cylinder head as well as those in the lower region of the cylinder space are important for the prediction of air flow in an actual engine cylinder. Transition of the angular momentum flux along the cylinder axis is considered to be influenced by three kinds of angular momentum flux which is induced by an air jet around the inlet valve.