Mothers whose infants varied in early biological characteristics (born at term, n = 120; born at very low birth weight [VLBW], n = 144) were randomized to a target group (n = 133) or developmental feedback comparison group (n = 131) to determine whether learning responsive behaviors would facilitate infant development. The target condition included videotaped examples, problem-solving activities, and mothers' critique of their own behaviors through video procedures across 10 home visits. All target versus comparison mothers showed greater increases across multiple responsiveness behaviors observed in 4 assessments conducted across 6-13 months of age; changes in emotionally supportive behaviors were strongest for target mothers of infants born at VLBW. Increased maternal responsiveness facilitated greater growth in target infants' social, emotional, communication, and cognitive competence, supporting a causal role for responsiveness on infant development. Although benefits were generally comparable across risk groups, aspects of social and emotional skills showed greater change for those born at VLBW. Evidence for responsiveness as a multidimensional construct was provided as well as the importance of different aspects of responsiveness mediating the effect of the intervention on different infant skill domains.