This research project, which is the first stage of a five-year longitudinal study, was designed to investigate infants' and toddlers' social interactions with a baby in a group care setting. The 15 children ranged in age from four (4) to 42 months. A target infant, ranging in age from three (3) weeks to two (2) months, was placed in a specified observational area in a playroom and a behavioral checklist was used by trained observers to record interactions. Results showed that toddlers' interactional behaviors toward an infant increased significantly at 18 months and older. At all ages, females demonstrated more social interactive behaviors than males. When the behaviors were grouped into categories of comforting, sharing, and cooperation, significant differences were found by age and by sex. Infant and toddler behaviors can be mediated and expanded upon by a caregiver who is knowledgeable and responsive to these beginning social interactions.