The Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD) was funded as part of a National Institute of Mental Health initiative to develop effectiveness information about treatments, illness course, and assessment strategies for severe mental disorders. STEP-BD studies were planned to be generalizable both to the research knowledge base for bipolar disorder and to clinical care of bipolar patients. Several novel methodologies were developed to aid in illness characterization, and were combined with existing scales on function, quality of life, illness burden, adherence, adverse effects, and temperament to yield a comprehensive data set. The methods integrated naturalistic treatment and randomized clinical trials, which a portion of STEP-BD participants participated. All investigators and other researchers in this multisite program were trained in a collaborative care model with the objective of retaining a high percentage of enrollees for several years. Articles from STEP-BD have yielded evidence on risk factors impacting outcomes, suicidality, functional status, recovery, relapse, and caretaker burden. The findings from these studies brought into question the widely practiced use of antidepressants in bipolar depression as well as substantiated the poorly responsive course of bipolar depression despite use of combination strategies. In particular, large studies on the characteristics and course of bipolar depression (the more pervasive pole of the illness), and the outcomes of treatments concluded that adjunctive psychosocial treatments but not adjunctive antidepressants yielded outcomes superior to those achieved with mood stabilizers alone. The majority of patients with bipolar depression concurrently had clinically significant manic symptoms. Anxiety, smoking, and early age of bipolar onset were each associated with increased illness burden. STEP-BD has established procedures that are relevant to future collaborative research programs aimed at the systematic study of the complex, intrinsically important elements of bipolar disorders.