This study was designed to investigate (1) the construct validity of a measure of the mother's internal representation of herself as a secure base in samples of married and divorcing mothers and infants, and (2) the relative contribution to infant security of this measure and a second representational measure, termed Psychological Protection, which focused specifically on the mother's responsiveness to the infant in the context of father visitation. There were 144 mothers and their first-born infants, age 12 to 20 months, who participated in the study. Of these, 51 dyads were from intact families; 93 were from families who had never married, had recently separated, or were in the process of divorce. Divorcing families were further divided into those in which the infant was participating in overnight timesharing arrangements with the father (n = 44) and those in which the infant was not (n = 49). Mothers completed questionnaires, they participated with their infants in the Strange Situation, and an hour-long, semi-structured Caregiving Interview was administered to them. Ratings of mothers on the Secure Base and Psychological Protection scales were based on verbatim transcripts of this interview. As predicted, mothers of securely attached infants in all family groups were discriminated from mothers of insecurely attached infants on the basis of Secure Base scores. Within the group of divorcing mothers, Secure Base scores were correlated with a rating of the mother's Psychological Protection of the infant in the context of visitation and both measures made independent contributions to infant attachment security. These findings are interpreted in terms of a more general model of the caregiving system. The manner in which the divorce context can disrupt the mothers' caregiving behavioral strategies and representations is also discussed.