This study examined the reactions of 45, 10-month-old infants to peer strangers. The infants were observed in two conditions: with a stranger of the identical age (10 months) and with one who was younger (5 months). In additon, each infant's behavior when he was alone with his mother was compared to his behavior when he was in the presence of strangers. There were no significant differences between the infants' responses to the 5-month-old and 10-month-old strangers. However, in the presence of strangers, infants looked at their mothers less frequently and looked instead at the strangers; vocalized less frequently but did not fuss or cry more often; did not stay as close to their mothers but were less active; and smiled more frequently and sooner. Results indicate that infants are not necessarily fearful of strangers. They may, in fact, respond to strangers in a curious, friendly, and positive manner, particularly if the strangers are peers. (JMB)