After participating in this activity, learners should be better able to:• Evaluate factors that have been identified in prospective studies as predicting the onset of bipolar disorder ABSTRACT: The prodromal phase of bipolar disorder (BD) remains incompletely characterized, limiting early detection of BD and delaying interventions that might limit future morbidity and disability. Retrospective and family-risk studies have consistently found evidence of prodromal psychopathology in subjects later diagnosed with BD. Here, we review prospective studies of clinical risk factors and exposures identified before diagnosis of BD: our findings are consistent with those from retrospective and family-risk studies. Affective psychopathology often precedes diagnosis to suggest a homotypic trajectory in developing BD. Early non-affective (heterotypic) psychopathological disturbances, including anxiety and disruptive behavior disorders, as well as environmental factors and exposures, have been found in prospective studies to increase the risk of BD, but tend to lack specificity in predicting BD. Findings from prospective studies are encouragingly similar to those of retrospective and family-risk studies.