To investigate whether each of three DSM-III-R phobic disorders (simple phobia, social phobia, and agoraphobia with panic attacks) is familial and "breeds true."Rates of each phobic disorder were contrasted in first-degree relatives of four proband groups: simple phobia, social phobia, agoraphobia with panic attacks, and not ill controls. Phobia probands were patients who had one of the phobia diagnoses but no other lifetime anxiety comorbidity.We found moderate (two- to fourfold increased risk) but specific familial aggregation of each of the three DSM-III-R phobic disorders.These results support a specific familial contribution to each of the three phobia types. However, conclusions are limited to cases occurring without lifetime anxiety comorbidity and do not imply homogeneity within categories.