Reiss's expectancy theory states that panic attacks, phobias, and other fear reactions arise from three fundamental fears (sensitivities): anxiety sensitivity, fear of negative evaluation, and injury/illness sensitivity. The present study examined two central aspects of the theory: (1) the assumption that fundamental fears are factorially distinct, and (2) the proposition that fundamental fears account for variance in other forms of fear and in trait anxiety. Measures of fundamental fears, common fears, and trait anxiety were administered to 100 community volunteers. The results supported Reiss's theory; the fundamental fears were factorially distinct, minimally intercorrelated, and accounted for significant proportions of variance in measures of other fears and trait anxiety. Specific and conceptually meaningful links were found between fundamental fears and common fears.