Examined preschoolers' stress reactions to standardized peer entry paradigm and relation to temperament, observed approach to peers, and self-perceived peer competence. Found that 4-year-olds showed significantly less new peer avoidance, higher ratings on approach temperament, and larger physiological stress reactions than 3-year-olds. Discrepancy between self-reported peer competence and behavior in peer entry situation was associated with larger stress responses. (Author/KB)