The significance of prenatal and perinatal complications (biological risk) and of family adversity (psychosocial risk) on early child development was examined in a prospective study. Developmental outcome of 350 infants was assessed by measures of motor, cognitive, and social-emotional functioning at 3, 24, and 54 months. Results indicated a differential impact of risk factors on specific outcomes. Whereas psychosocial risks became more prominent with growing age and were related to poorer child outcome in all areas of functioning, biological risks decreased in influence and predominantly resulted in poorer motor development. The contributions of biological and psychosocial risks on outcomes were additive. A number of individual risk factors emerged as significant predictors of later maladaptation.