The present study explored the validity of the unipolar-bipolar distinction in the characterological mood disorders. Thirteen cyclothymic and 32 primary early-onset dysthymic outpatients, diagnosed according to DSM-III-R, were compared on demographic, clinical, personality, and family history variables. The cyclothymics exhibited significantly higher levels of depressive symptomatology and extraversion and had a higher rate of bipolar I disorder in their first-degree relatives than the dysthymics. In addition, a significantly greater proportion of cyclothymics than dysthymics had a family history of drug abuse. The groups did not differ significantly on gender, overall rates of affective disorders in relatives, or a number of symptoms which have been reported to distinguish unipolar and bipolar depressives. Although these data require replication due to the small sample and large number of analyses conducted, they provide at least partial support for extending the unipolar-bipolar distinction to the characterological mood disorders.