We present the results of a study of the catalyst loading behavior on the "catalyst-trap" microreactor, a novel microreactor recently reported by McGovern et al. (2008) [1]. The study focuses on the important issue of catalyst deployment inside microscale reactors which must be understood in order to further the implementation of emerging microtechnology for organic chemical synthesis. We initially set out to use the catalyst-trap microreactor to investigate the catalytic hydrogenation of 3-nitrotoluene. In that investigation a 100% yield was fortuitously achieved due to the activity of the reaction. However, the low trap occupancy ratio (20% of the traps had been loaded) could still be an impediment, especially for other more complex reactions. After extensively studying the loading procedure, 98% of the traps in the reactor were able to be successfully loaded. Simulations based on a random-walk model and the procedures of the loading experiments were conducted to better understand the filling mechanism. We found the physical catalyst loading procedure was consistent with the simple mechanism in our simulations. Through this work, catalytic area and catalytic efficiency have been significantly increased, and the synthetic capability enhanced as a result. (C) 2009 Elsevier B.V. All rights reserved.