Emotions run high when it comes to bipolar disorder (BD) in children. At conferences in the recent past, I often had to speak in front of audiences that were divided into those who strongly favoured a wider use of the diagnosis of BD and those who fervently opposed it. For years, such diametrically opposed views have been held with equal vigour, despite the striking absence of much evidence either way. This is about to change as more empirical data on BD are accumulating. It is research like that conducted by Boris Birmaher's group that allows us to start having a more rational discussion on youth BD, and a debate that goes beyond anecdote and prejudices. In this Commentary I highlight the ground-breaking research in the US of studying the clinical course of BD and translate the impact of these findings for the diagnosis and treatment of children and adolescents on this side of the Atlantic.