Social interactions are important correlates of physical activity in children. Previous studies used global measures; the present study examined the influence of specific social interactions on immediate physical activity in children with data obtained from the Behaviors of Eating and Activity for Child Health: Evaluation System (BEACHES). The study examined parental and peer prompting of physical activity at home among 178 Mexican-American and 113 Anglo-American children at age 4 years and again at age 6.5 years. Most activity prompts came from adults interacting with children when they were sedentary. A reduction in the frequency of prompts from baseline to follow-up occurred in the prompter group (adult or child peer), gender, ethnicity, and preprompted activity level categories. Children's responses to these prompts showed that as they aged, they seemed to rely less on the interpersonal (especially adult) aspects of their environment for cues to be more active.