Bipolar disorder is a severe and chronic illness associated with significant occupational and social impairment, enormous public health costs, and high rates of suicide. The single most potent risk factor for the development of bipolar disorder is a first-degree family member with the illness; indeed, offspring of parents with bipolar disorder are a particularly high-risk group who typically display early onset and severe course of illness. Thus, early assessment and intervention for the children of parents with bipolar disorder focused on specific, measurable, and modifiable risk factors has the potential to prevent or ameliorate the progression of bipolar disorder in those at highest risk.