Children of depressed parents are at increased risk for depression and other developmental problems. Recent research indicates that disturbances exist in face-to-face interactions between depressed mothers and their infants. In the present study, the effects of maternal depression on motherese, an interactive behavior that plays a significant role in affective, cognitive, and social development, were examined. 2 paralinguistic features of motherese were examined: temporal parameters of utterances and pauses and the frequency of use of 5 types of intonation contours typically found in motherese utterances. Face-to-face interactions between 36 mothers and their 3-4-month-old infants were audio-recorded, and hard copy records of pitch contours and relative intensity were produced for 2-min interaction sequences. Results indicated that depressed mothers failed to modify their behavior according to the behavior of the infant. They were significantly slower to respond to an infant vocalization, had more variable utterances and pauses, and were less likely to utilize the exaggerated intonation contours that are characteristic of motherese. The results provide evidence for a mechanism through which maternal depression increases the infant's risk for psychopathology.