The effect of liquid maldistribution on reaction in a trickle-bed reactor is examined by using a discrete model. It is based on a computergenerated, two-dimensional bed packed with equal-sized spherical catalyst pellets. The configuration of the liquid inlet distributor is included in the model. The flow on and intraparticle diffusion and reaction in each and every catalyst pellet are sequentially analyzed, leading to predictions of the overall reactor behavior. The interplay between flow patterns, wetting on individual pellets, and effectiveness enhancement is demonstrated. The present model offers advantages over other conventional models in terms of overall reaction rate predictions, the ability in the description of irregular morphological features, the absence of the artificial backmixing of materials, and others. © 1990, American Chemical Society. All rights reserved.