People seem to differ in their conditionability, that is, the ease by which fear associations (neutral stimulus-unconditioned stimulus [CS-US] contingencies) are learned. Recently, the level of trait worry has been proposed as a predictor of heightened conditionability. The current research aimed to (a) further investigate this influence of individual differences in trait worry on the strength of fear acquisition, (b) explore whether this association could be explained by trait anxiety, and (c) assess possible underlying mechanisms of this relationship. In a nonclinical sample, the amount of trait worry predicted heightened conditionability in a differential fear conditioning paradigm, both in fear ratings and in performance on a secondary probe reaction time task. A significant correlation was observed for general conditioning to the CS+ and also for differential conditioning (taking into account excitatory and inhibitory responding) in Experiment 1. These associations could not be fully explained by trait anxiety. US inflation and strengthening of the CS-US contingency through rehearsal are discussed as possible underlying mechanisms. (Contains 4 notes and 3 tables.)