The purpose of this study was to describe the pattern in which English-speaking children acquire intonation. A second goal was to account for emerging intonation from a theoretical perspective. Six groups of 10 children each between the ages of 6 and 23 months participated in individual play sessions with their mothers and an experimenter. Pitch contours were acoustically analyzed in monosyllabic utterances produced by each child. The observed nonlinear shape of intonation development suggested a linguistically based pattern of regression and reorganization. However, the precocious expression of intonation in the youngest infants also pointed to the role of physiological universals and emotional experience. It is concluded that children's early intonation reflects biological, affective, and linguistic influences.