The precise characterization of microgeometries is a crucial task in the study of flow phenomena at these scales. Since the use of conventional optical microscopes is somehow limited in terms of accuracy, the present work studies the use of micro-PIV measurements to characterize a rather irregular microchannel cross-section. The micro-PIV is employed with a spatial resolution of 23.68 mu m x 23.68 mu m allowing for the location of the microchannel walls with an accuracy, in average, 10 times higher than that provided by the use of a conventional optical microscope. The accuracy of the micro-PIV results was validated by comparing the volumetric flow rate yielded by the integration of the micro-PIV velocity profiles against that supplied by the syringe pump employed in this experimental work. The 3% difference revealed the good quality of the measurements, demonstrating the potential of the micro-PIV technique to characterize both the flow kinematic parameters and the enclosing geometry. (C) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.