A particle trajectory in a turbulent flow is measured by a 3-dimensional tracking technique and compared with the pattern calculated by a Lagrangian model. The geometry chosen is a standard vessel provided with a Rushton turbine. First, the flow field is simulated using the commercial Fluent package. The impeller global performance is determined. The dimensionless numbers are calculated: t(c), N-QB N-B. These results are validated by LDV data. The numerical particle trajectory is compared to the experimental trajectory, and the reliability of the numerical trajectory is proved. Finally, some news tools for analyzing the flow are presented. Useful information is included in the long particle trajectory, which enables one to compute a probability of presence. The fluid dynamic behavior is visualized by Poincare sections.