Children’s activity level is commonly thought to be a stable characteristic, but considerable evidence exists in the literature for situational influences. Two studies are reported in this paper. First, preschool children who had been observed when toddlers participated in a study to evaluate the consistency of their motor activity level over time and across situations and to evaluate associations between high levels of motor activity and other dimensions of temperament. Second, the relations among several measures of activity level and ratings of problem behavior in toddler-age boys and girls were examined. Activity level was stable when measured by the same situation, but not across methods or across situations. Girls, but not boys, rated high on activity level received positive ratings on temperament variables. Boys, but not girls, rated high on activity level were rated by parents and teachers as showing more problem behaviors.