A novel technique is used to obtain the distribution of particle wetting in trickle-bed reactors for different flow and prewetting conditions. Two prewetting methods were investigated: (1) Levec prewetting, in which the packed catalyst bed is completely flooded and then left to drain before steady state trickle-flow is commenced; (2) Kan prewetting, in which the bed is prewetted by pulsing with the liquid before flow, after which the liquid flow is gradually set back to the required rate. It is shown that the method of prewetting has a major influence on average wetting efficiency and wetting distributions: Average wetting efficiencies differ with as much as 20% between the prewetting modes, and Levec prewetting leads to a considerable fraction of the bed that is not used (up to 7% at the investigated flow conditions), whereas the entire catalyst is used in Kan prewetted beds. It is shown that the particle wetting distributions can influence the modeling of Levec prewetted beds for liquid- and gas-limited conditions. (c) 2006 American Institute of Chemical Engineers.