This comprehensive study of mutual responsiveness examined 102 mothers and 102 fathers interacting with their children at 7 and 15 months. Responsiveness was studied from developmental and individual differences perspectives, and assessed using macroscopic ratings and microscopic event coding. The latter captured parents' reactions to children's negative, positive, and physical bids, and children's reactions to parents' social-interactive bids, mood regulation attempts, and influence attempts. Responsiveness depended on bid type and child age, and reflected developmental changes in children, parents, and relationships. Mothers were more responsive than fathers; children were equally responsive to both parents and coherent in their responsiveness. Ratings revealed dyadic mutuality and longitudinal continuity of responsiveness. Parent-child responsiveness from 7 to 15 months was consistent with assumptions of a parent-driven process.