This study investigated whether the interactions of biological mothers and their offspring differ from those of institutional caregivers and infants in their charge. The subjects--43 three-month full-time Greek infants (22 home-reared infants and 21 from the institution, Babies' Center Metera) were studied while interacting with their primary caregiver. In a 30-minute observation period, timed observations 10 seconds in duration were made of infant behaviors, socializer behaviors, and mutual interactions. Findings showed that biological mothers rocked and touched their infants and vocalized in a face-to-face fashion significantly more than did caregivers. In contrast, caregivers provided more vocalization without establishing eye contact. Finally, institutional infants vocalized and fussed significantly less than home infants. Findings indicated that the rearing conditions in the two environments were different, a condition which may account for the frequently reported developmental delay of infants reared in institutions. (Author/RH)