The development of behaviour problems in infants born with biological risk (low birthweight) and psychosocial risk (psychosocially disadvantaged family) was studied in a sample of 347 children (171 males, 176 females) at the ages of 2, 4:6, and 8 years. In the search for factors that moderate the effects of early risks, the role of early responsive caregiving was examined. Results indicate that infants at psychosocial risk exhibited both more externalizing and internalizing problems across ages than infants not at psychosocial risk, while no overall differences were apparent between normal- and low-birthweight groups. With one exception, no interactions between biological and psychosocial risk factors emerged, suggesting that their simultaneous effect is largely additive. Maternal responsivity was found to moderate the effects of low birthweight on hyperkinetic and internalizing problems as well as to influence the consequences of family disadvantage on total problems. These findings stress the importance of early parenting in the behavioural development of at-risk children.