The purpose of this study was to provide a description of the kinds of prosocial behavior that 2- and 5-year-old children naturally exhibit. Caretakers were asked for their observations of children's prosocial behavior in natural settings. Specifically, 40 parents and teachers who had daily interactions with 2-year-olds were asked to name the most prosocial 2-year-old they knew and give a detailed written description of those behaviors of the child which had caused them to make the nomination. The same procedure was undertaken with 37 caretakers of 5-year-olds. Lists of 20 attributes of prototypically prosocial 2-year-olds and 24 attributes of 5-year-olds were generated. Findings revealed considerable variability in the attributes mentioned by the caretakers. Similarities between the two age groups were more pronounced than differences. Range of behavior was similar at both ages. Core attributes were quite similar for each age, but developmental differences appeared in less central attributes. Although the same attribute may describe children at different ages, the specific behaviors through which that attribute is manifested may differ at each age. Cluster analysis suggested that there are six major clusters in adults' conceptions of 2-year-olds' prosocial behavior and five in their conceptions of 5-year-olds'. (RH)