Abstract. Model checking and simulation tools based on the colored Petri nets formalism spend a significant amount of time in performing enabling tests. This consists in taking into account the color mappings of the net to determine valid transitions variables assignments at a given marking. This work proposes an algorithm for the enabling test problem. It implements the relations of conflict and causality between transitions to efficiently maintain a set of enabled transitions. This set is updated during the search algorithm according to the transitions fired (or unfired). However, in most cases this approach is not sufficient to compute the set of enabled transition bindings, and has to be followed by a unification algorithm. This is the objective of the second part of this work.