A cellular automata model for liquid distribution studies in trickle bed reactors is presented. It is a potential tool for describing non-uniform distribution of gas and liquid in a trickle bed. This non-uniformity may arise from a wide range of potential sources, such as improper distribution of the feed, random or radial porosity variation, wall effect, partial wetting of the catalyst, and gas-liquid surface tension related effects. Axial and radial dispersion of the liquid flow are inherently included in the model, since the fundamental model probability parameters are directly related to the dispersion coefficients. The present model is extremely fast due to simple single-event modeling, and it is well suited for parallelization. Three examples of the model performance are shown. In the first a liquid jet spreading from a point source is followed, and in the second, effect of radial porosity profile to wall flow is examined. The third example illustrates the potential of the model to predict pulsing flow regime. (c) 2006 Elsevier Ltd. All rights reserved.