The capabilities of 3-D-Particle Tracking Velocimetry (PTV) to measure flow fields during the blending of Newtonian and non -Newtonian fluids in a standard baffled cylindrical vessel are assessed. The results are benchmarked against conventional 2-D Particle Image Velocimetry (PIV) data. The vessel, of diameter T = 0.19 m, is equipped with a 6-blade down-pumping PBT impeller of diameter, D = 0.5T. Experiments in the low transitional (Re 70), and transitional (Re 1000) regimes have been conducted, using a range of Newtonian and non-Newtonian fluids. Turbulent flow measurements (Re > 20,000) are made using Newtonian fluids. Data from both techniques are compared in terms of average flow field and, where appropriate, turbulent fluctuating velocity components. Particular emphasis is given on how comparisons can be made between the Eulerian Ply data and the Euler-Lagrangian PTV data. The overall results demonstrate the validity of the PTV technique in this application to acquire average flow fields which are in good agreement with PIV. Turbulent flow properties are less well resolved by PTV due in part to the large size of the tracer particle used. Other advantages and limitations of PTV versus Ply are also discussed. Crown Copyright (C) 2017 Published by Elsevier Ltd.