40 mothers and their 12-month-old infants were observed twice at home by 2 observers for 2 hours. After the second visit, the observers described the infant using the Waters Attachment Behavior Q-sort and the mother's interactive behavior with the Maternal Behavior Q-sort developed by the present authors and Ainsworth's rating scales. Maternal sensitivity was unrelated to maternal age, income, or SES, but correlated positively with maternal education. Mothers of more difficult children were less sensitive. A strong relation was found between infant attachment and maternal sensitivity as measured by the Maternal Behavior Qsort and by the Ainsworth scales. Using the Q-sort procedure, mothers of more secure infants were more frequently characterized as noticing their babies' signals and using these signals to guide their behavior; they also were more knowledgeable about their infant and appeared to enjoy them more than mothers of less secure infants.