The Epidemiologic Catchment Area community sample data were analyzed to determine whether there is a general tendency for subjects with two or more disorders to have an earlier age of onset of the index disorder than subjects with only one disorder. DSM-III axis I disorders and antisocial personality were each used as index disorders in separate logistic regressions. The results show that an earlier age of onset is associated with greater comorbidity in major depression, with a similar trend for alcoholism. Schizophrenia and the phobias, however, showed significant results in the opposite direction. Overall, the results argue for specific rather than general effects of age of onset on comorbidity.