This study evaluated three interrelated hypotheses conceming separation between anxiety sensitivity (AS) and trait-anxiety and how specífic AS dimensions predicts fear. A sample of 910 undergraduates completed a psychometric assessment package that included the Spanish version ofthe Anxiety Sensitivity Index (ASI; Reiss et al., 1986; Sandin et al., 2004) and measures of fears, anxiety, depression and personality. AS was analyzed at the le veIs ofthe total sca/e and the three ASI-subsca/es (Physica/-, Cognitive-, and Socia/-Concems). The ASI was found to be statistically the best predictor, accounting for fears aboye and beyond the vanance accounted for by the remalning variables. The Physical Concems subsca/e was predictive of agoraphobic and blood-injection-injury fears, whereas the Social Concems subsca/e predicted social fears. Findings were discussed in relation to (1) separation befween AS and trait-anxiety, (2) differential predictive validity of AS, and (3) predictive validity ofthe Spanish version of the ASI.