ABSTRACT A trait approach to personality has many implications for psychotherapy. Given that traits contribute to the expression of symptoms of common psychiatric disorders, are moderately heritable, and relatively stable (yet also dynamic to some extent), long-term change in symptoms is possible but is likely to be limited. Analogous to the manner in which genes set the reaction range for phenotype, standing on certain traits may set the patient's “therapeutic range.” On the other hand, some of the same traits that may limit the depth of therapeutic benefits might also increase their breadth. In addition, taking the patient's standing on different traits into account can inform the choice of therapeutic strategy and targets and can affect the formation of the therapeutic alliance and compliance with self-help exercises. Finally, other aspects of personality beyond traits, such as ego development and narrative identity, also appear to have important implications for psychotherapy.