Fear and anxiety are poorly delineated in much of the clinical and research literatures. Although some theorists and researchers have posited explanations for how trait fear and trait anxiety differ, many others conceptualize the constructs as largely or entirely interchangeable. The primary goals of this review are to examine clinical conceptualizations and neurobiological studies of fear and anxiety, examine the animal and human literatures on the correlates of fear and anxiety, provide clearer definitions of these two constructs, and discuss their implications for psychopathology. A secondary goal is to evaluate content of self-report measures of trait fear and anxiety, and meta-analyze the relations between self-reported trait fear and anxiety. We found that existing measures share significant content overlap across constructs. Despite this overlap, our meta-analysis revealed only a moderate (r=0.32) relationship between measures of trait fear and anxiety, with an even lower relationship (r=0.14) when we examined trait fear measures operationalized in terms of harm avoidance. These findings suggest that fear and anxiety are largely distinct emotions, and that psychological disorders of trait fear and trait anxiety warrant classification in separate higher-order categories. Moreover, they suggest that future research should focus on deriving more content valid measures of trait fear and trait anxiety from the neurobiological and diagnostic literatures.