The authors review the various clinical and experimental studies of children of parents with affective illness, spanning infancy, childhood, and early adolescence and including their own and the studies reported in this Special Section of the Journal. They find a clear tendency to early disturbances in these children that seems related to adult affective illness in the areas of affect regulation and social interaction. Although these findings suggest a developmental line of affective illness linking child and adult forms, many issues need further clarification.