The high rate of psychosocial problems in offspring of affectively ill parents has been established, although the developmental timing of these problems and the synchronous occurrence of the symptom clusters in parent and offspring have not been systematically examined. This study follows the course of children's psychosocial development over time in relation to the course of parents' illness (timing of episodes, severity, treatment, family context), in order to investigate the interdependencies among level of children's development, children's problems, family environment, and parents' manifestations of affective illness.