Nitrobenzene hydrogenation over palladium catalyst was performed in a microstructured falling film reactor at a range of flowrates (0.5-3 ml/min) and pressure (1-6 bar). Confocal microscopy was used to measure liquid film thickness. Comparison with film thickness prediction equations showed an overprediction of 10-30%. The k(L)alpha of this system was estimated to be 3-8 s(-1) with interfacial Surface area per reaction volume 9000-15000 m(2)/m(3). Conversion was found to be affected by both liquid flowrate and hydrogen pressure, and the reactor operated between the kinetic and mass transfer controlled regimes. (C) 2004 Elsevier Ltd. All rights reserved.