This study examined the effect of a day care program on mother-child interaction patterns and attachment behaviors, and compared these patterns of behavior with those obtained from a matched sample of more advantaged home-reared infants. Subjects were 60 infants, ranging in age from 3 1/2 to 9 1/2 months, and their mothers. There were three groups of mother-infant dyads: (1) the high-risk experimental group (HRE), comprising 15 high-risk infants who had attended a day care facility for 8 hours per day since they were approximately 2 months of age, and their mothers; (2) the high-risk control group (HRC), comprising 15 high-risk infants and their mothers living together at home; and (3) 30 dyads selected at random from birth records for the local community. Data were collected by home observation and by interaction process analysis of 25-minute videotapes of mother-child interaction in a home-like laboratory setting. Results indicated that infants in the HRE group vocalized more and were generally more responsive than infants in the HRC group; these findings reflected basic differences in the infants rather than in the mothers, who differed only on measures of maternal concern for optimal child development. The HRE infants and their mothers were found to have a similar social relationship to that between infants and mothers in the general population group, suggesting that intervention has a positive effect on mother-child interaction in disadvantaged families. (GO)