Recent evidence has highlighted suicidal risk associated with bipolar disorder (BD). Using a family risk approach, the goal of this study was to evaluate suicidal thoughts and behaviors longitudinally from childhood to young adulthood in children of mothers with BD, Major depressive disorder (MDD), and well mothers. Few group differences were found for cross-sectional assessments of suicidal thoughts and behavior in young adulthood; the offspring of MDD demonstrate an earlier onset and more persistent suicidality than other groups, but by young adulthood, BD offspring appear to be comparable to MDD offspring in their rates of suicidality. The longitudinal assessments reveal a pattern of higher suicidal risk in MDD offspring, more intermediate risk in BD offspring, and lower risk in well offspring. Precursors and correlates of suicidal thoughts and behaviors were also examined. These findings suggest diverse developmental trajectories based on family risk and have implications for planning preventive intervention. © 2008 Wiley Periodicals, Inc. J Clin Psychol 64: 531–540, 2008.