Bipolar spectrum disorders and addiction often co-occur and constitute reciprocal risk factors that the authors believe are best considered under a unitary perspective. In particular, we submit that patients whose disorders fall under the bipolar spectrum - and its hyperthymic and cyclothymic temperamental substrates are at increased risk for substance use, possibly moving towards addiction through exposure to intrinsically dependence-producing substances. In our experience, the contribution of bipolar spectrum disorders to the addictive process is often clinically missed, because attenuated and subclinical expressions of such mood disorders as bipolar II and cyclothymia are not adequately appreciated by our current formal diagnostic system (e.g. DSM-IV, as well as research and clinical practice based on it). The use of agonist treatment in dual diagnosis heroin addicts has allowed us to gather valuable knowledge about the intrinsic, and historically and clinically documented mood-regulating effects of opiates. From the therapeutic point of view, the challenge of double diagnosis requires double competence from clinicians. The combination of opiate agonists and mood stabilizers often produces results difficult to obtain with the use of the two types of drugs separately. We therefore submit that the present conceptualization of the link between bipolar spectrum and addictive disorders has not only heuristic and scientific values, but also an important message for the clinician.