This study concerns pressure drop in a two-phase heat sink containing an array of staggered square micro-pin-fins having a 200 x 200 mu m(2) pin cross-section by a 670 mu m pin height. Three inlet temperatures of 30, 60 and 90 degrees C, and six maximum mass velocities for each inlet temperature, ranging from 183 to 420 kg/m(2) S, were tested. Frictional pressure drop in the boiling region is deemed the dominant pressure drop component. The Lockhart-Martinelli correlation for laminar liquid-laminar vapor combination in conjunction with a previous single-phase friction factor correlation can adequately predict the data. Micro-pin-fins offer better flow stability than parallel micro-channels. (C) 2009 Elsevier Ltd. All rights reserved.