In contrast to recent experimental studies that have sought to establish the infant's ability to imitate, the goal of the current study was to establish the actual performance of imitation by infants and their mothers during episodes of face-to-face play. Three-min play episodes of 20 mothers and their 13- to 16-week-old infants were videotaped. Instances of mouth openings, lip movements, tongue protrusions, smiling, and vocalizations by both partners were coded. Sequential analyses revealed stochastic patterns of imitation by both interactants. Mothers contingently imitated initiations by their infants and were more likely to make like initiations during action in the same category by their infants. Infants did not show onset-to-onset imitation but did show an increased likelihood to initiate actions when their mothers were engaged in a like action. That imitation by the mother is a pervasive characteristic of such interactions is consistent with earlier suggestions of its role in the acquisition of social and emotional skills. The results suggest that infants also display patterns of matching in early social interactions.