The trajectory of tracer particles of size 50 +/- 5 mu m has been measured with positron emission particle tracking (PEPT). Resin particles were labelled with 0.05-0.5 MBq of Ga-68 via ion exchange mechanisms. Their position was measured in a variety of PEPT experiments: at rest; rotating in fixed circular trajectories in air and in water, and moving freely in a Rushton stirred vessel. The uncertainties in the measured locations are of the order of 2.6 mm for the measurements presented. The experiments were facilitated by new techniques in tracer labelling and handling, along with a high number of detector elements in the ECAT 'EXACT3D' PET scanner at PEPT Cape Town. This opens the way for PEPT studies to explore fine particle technologies, such as froth flotation and slurry flow. (c) 2012 Elsevier Ltd. All rights reserved.