This study was intended to determine whether differences in maternal attitude and behavior relate to differences in infants' Strange Situation security classification. Subjects for the present study were 38 white middle-class mothers and their normal, 1-year-old infants (20 male, 18 female). Infants who were classified as to the quality of their attachment relation to their mothers at 12 months in the Strange Situation were seen nine months later in a free play session with their mothers. Results showed that infants judged more secure at 12 months had mothers who (when their infants were 21 months) were judged significantly more sensitive, more accepting, and were more expressive of positive affect than mothers of insecurely attached infants. Also, mothers of insecurely attached infants showed significantly more anger than mothers of securely attached infants. It was found that differences in infants' apparent security at 12 months can be meaningfully related to differences in mothers' social and affective behavior nine months later. (Author/MS)