Objectives: Current clinical and epidemiological research provides support for a continuum of bipolar psychopathology: a bipolar spectrum that ranges from subclinical manifestations to full-blown bipolar disorders. Examining subthreshold bipolar symptoms may identify individuals at risk for clinical disorders, promote early interventions and monitoring, and increase the likelihood of appropriate treatment. The present studies examined the construct validity of bipolar spectrum psychopathology using the Hypomanic Personality Scale. Methods: Study 1 used interview and questionnaire measures of bipolar spectrum psychopathology in a sample of 145 nonclinically ascertained young adults. Study 2 assessed the expression of the bipolar spectrum in daily life using experience sampling methodology in the same sample. Results: In study 1, Hypomanic Personality Scale scores were positively associated with clinical bipolar disorders, bipolar spectrum disorders, the presence of hypomania or hyperthymia, depressive symptoms, poor psychosocial functioning, cyclothymia, irritability, and symptoms of borderline personality disorder. In study 2, bipolar spectrum psychopathology was associated with negative affect, thought disturbance, risky behavior, and measures of grandiosity. These findings remained independent of clinical bipolar disorders. Conclusions: In the present studies, bipolar-like disruptions in cognition, affect, and behavior were not limited to clinical diagnoses or mood episodes, providing further validation of the bipolar spectrum construct. The bipolar spectrum model appears to provide a conceptually richer basis for understanding and ultimately treating bipolar psychopathology than current diagnostic formulations. © 2012 Elsevier Inc.