Bipolar spectrum disorders are characterized by highs and lows of mood, energy, motivation, cognition, and activity. The behavioral approach system (BAS) dysregulation theory provides an integrated model for understanding psychosocial and biological features of bipolar disorders. The theory emphasizes the role that sensitivity to rewards and goals plays in bipolar disorder. We review theory and evidence for the BAS-dysregulation model of bipolar disorders. We consider whether high BAS sensitivity is a correlate of, vulnerability factor for, and predictor of the course of bipolar spectrum disorders. We also discuss BAS-relevant life events as triggers of bipolar mood episodes. Finally, we address the implications of the BAS model for treatment and prevention of bipolar disorders and suggest directions for further research.