Two experimental techniques, direct sampling and in situ video microscopy, are used simultaneously to analyse evolving droplet size distributions in lean silicone oil-water dispersions in an agitated system of standard geometry. Samples withdrawn from the vessel at selected times throughout the agitation period were sized using standard microscopy and image analysis. A particle vision and measurement (PVM) probe (Lasentec) was used simultaneously to capture droplet images at the same relative position in the agitated vessel. Comparative trials encompassed a dispersed-phase viscosity range from 50 to 500 mPa s and levels of energy dissipation from 55 to 156 W kg(-1) in a standard tank of 0.157 m diameter. Close agreement between the distributions obtained using both techniques was observed across the full range of operating conditions with values of the Sauter mean diameter consistent to within 10%. In the case of the PVM system used here the relatively long image acquisition times preclude the use of the technique in following the rapid changes at the early stages in the evolution of a dispersion. The direct sampling method provided consistent reproducible results for the particular liquid-liquid combination used here; however, for larger density differences between the two phases care must be exercised to ensure that the extracted samples are truly representative of the local conditions in the agitated vessel. (c) 2004 Elsevier B.V. All rights reserved.