The roles of person familiarity and parental involvement in 3.5-month-old infants' sensitivity to the dynamic emotion expressions of others were explored. In the home, parental facial/vocal expressions (happy, sad, angry) were videotaped, and measures of parent-infant involvement were obtained. In the laboratory, 32 infants alternately viewed their mother and father and an unfamiliar woman and man portraying expressions in an intermodal preference task. Infants looked differentially at mothers' expressions but not at those of fathers or unfamiliar adults. Examination of parent-child involvement patterns revealed significant relations with infants' sensitivity to expressions. Results suggest that person familiarity may facilitate infants' developing understanding of others' emotion expressions, and that individual differences in family dynamics may be relevant to infants' patterns of responding.