Event-related potentials (ERPs) were recorded from 6-month-olds (N = 30) as they looked at pictures of their mother's face and a stranger's face. Negative component (Nc) and P400 component responses from the ERP portion of the study were correlated with behavioral responses of the infants during a separation from their mothers. We measured the mother-directed infant behaviors of distress and visual search for mother during separation in order to determine if they were predictive of infants' brain responses to pictures of the mother's face versus a stranger's face. These behavioral measures are important because they likely reflect the functioning of the emerging mother-child relationship and inform debates about interactions between social experience and face processing. Infant distress and visual search for mother during separation were predictive of face processing ERPs, and this relationship differed across mother and stranger face presentations. In particular, distress was associated with larger amplitude P400 and Nc responses to the mother's face, and visual search for mother was associated with longer P400 and Nc latencies to the stranger's face. Implications for the developing mother-child relationship and face processing system are discussed. (Contains 1 footnote, 3 tables, and 2 figures.)