This proposal is one half of a jointly proposed multicenter study by Drs. Barlow and Fyer who are submitting two separate but similar applications. The objective of the proposed study is to conduct a blind, controlled, direct interview family of DSM-III-R simple phobic disorder to investigate its familial transmission, heterogeneity with respect to subtype (e.g., animal vs situational vs blood injury), relationship to "subdisorder" irrational fears (i.e., irrational fears which do not meet disorder criteria due to lack of associated avoidance, impairment or endurance with dread) and to other DSM-III-R anxiety disorders. Risk for psychiatric disorder and symptoms of first degree relatives of simple phobia probands (SPD probands, combined two site N=120) will be compared to risk among similarly evaluated first degree relatives of never mentally ill controls. To determine if there is independent familial aggregation of the blood/injury, animal and situational subtypes, probands will be prospectively subtyped and risk for each subtype contrasted across the resulting relative groups and relatives of not ill control probands (NCP). To assess familial aggregation of "subdisorder" irrational fears (SIF) and their relationship to SPD, both the SPD and NCP proband groups will be subdivided by presence or absence of at least one simple irrational fear (SIF). Risks for SPD, SIF, both or neither will be contrasted across relatives of the four resulting proband groups (No APD/No SIF, SIF Only, SPD Only, and SPD+SIF). Familial psychopathology among relatives of SPD patient probands will also be compared to that of relatives of 60 untreated "community member" SPD probands. Our initial objective is to use the family study method to more clearly delineate etiologically valid boundaries both between SPD and other anxiety disorders as well as within the DSM-III-R SPD category itself. Our long term goals include the possibility that because of their discrete nature and common occurrence, careful study of simple phobic disorders and "subdisorder" irrational fears may lead to development of a unique model in which to investigate inter-relationships between neurophysiological variation, subjective affect and cognition, and development of normal and psychopathological fear and avoidance behavior.