Particle Tracking Velocimetry (PTV) has become a standard technique frequently applied in flow field diagnostics. This article presents a novel technique which combines the strength of well known 2-D PTV with stereo calibration and correlation techniques to obtain 3D Lagrangian velocity fields. The here presented stereo correlation technique is fundamental for 3-D PTV. In addition with a sub pixel precise stereo calibration technique it is possible to reconstruct, timely and spatially resolved, paths of particles representing the flow characteristic. The stereo correlation technique uses the resulting trajectories from PTV. Therefore 2-D trajectories instead of spatial position for single particles are correlated. This allows to keep the set-up simple with a minimum number of two cameras and also speeds up the 3-D evaluation compared to multiple camera set-ups. First results of flow visualisation with particles and air bubbles are presented.