This demonstration study examines the affective reactions of infants when they imitate or fail to imitate play behavior modeled by an adult. Subjects were twenty-four 18-month-old and twenty-four 24-month-old male and female infants. Each infant visited the laboratory twice with an inter-session interval of 48 hours. At each session, the infant engaged in 10 minutes of free play amid an array of 23 objects and then was asked to watch an adult play with the objects. The adult either scattered the objects or formally modeled three acts. Ten minutes of free play followed the last modeled act. Distress behaviors (fretting-crying and attempts to leave), language, and imitation of one or more of the modeled acts were recorded. Results indicated a substantial increase in distress for those subjects who failed to imitate. Distress decreased for those subjects who imitated. Distress did not occur when the infant imitated at least one act and rarely occurred when the children who observed the modeled acts were younger than 15 months or older than 30 months of age. Further, 50% of the 24-month-old children showed deferred imitation over the 48-hour interval between sessions by imitating in the second session acts modeled in the first. These results are discussed briefly in terms of the child's development of standards. (Author/RH)