The objective of the work presented in this paper is to trace the interaction of two fluids in a sequence of 3-D images obtained with a system based on a high-speed solid state camera. The application background is the examination of the efficiency of a chemical mixing process under turbulent flow conditions, focussing on the finest scales of turbulence (Kolmogorov scales). Image processing and digital photogrammetric concepts are combined for 3-D voxel image sequence analysis. Specifically we describe the imaging process and particularities related to the capture of quasicontinuous voxel data sequences, and then we focus on theoretical and implementational issues associated with feature tracking in 3-D image sequences. We present an extension of least squares matching from 2-D images and pixels to 3-D images and voxels. The use of additional constraints of radiometric and/or geometric nature strengthens the matching solution. In addition, we discuss an efficient matching strategy, an important issue when considering the large amount of data and high velocities involved.