The effectiveness of social buffering in regulating stress appears to wane for a period with puberty at the same time that stress-reactivity increases and young adolescents become more vulnerable to stress-related affective pathology. However, there is a dearth of knowledge regarding the neural underpinnings of social buffering in children and the changes in neural responses to potential social buffers with puberty. Two of the proposed experiments address this gap in knowledge. In addition, to date, the loss of social buffering effectiveness with puberty has primarily been examined using activity of the hypothalamic-pituitary-adrenocortical (HPA) axis as the stress measure. All three proposed experiments will examine the pervasiveness of the effect by examining sympathetic and parasympathetic responses, in addition to salivary cortisol. Urinary oxytocin will also be examined because of its role as an anti-stress hormone. Finally, the effectiveness of parents and friends as social buffers during the peripubertal period has only been examined for social evaluative stressors. The proposed experiments will determine whether the loss of social buffering also extends to threat stimuli as it does in adults and to situations in which two friends are both experiencing the stressful event together. Finally, all three proposed studies will explore whether puberty is associated with an emergence of sex differences in social buffering by parents and friends. Participants will be 11-14 years old and Tanner staging by nurse exam along with self-report and testosterone and DHEA will index pubertal status. Our prior research uncovered the waning of the effectiveness of parents to serve as social buffers of the HPA axis over the pubertal transition and the concomitant failure of friends to “step in” as stress buffers. The proposed experiments are the logical extension of this work. The results will have the potential to drive significant attention to the role of developmental disruptions in social stress buffering as possible contributing factors in the rise of affective problems in the early teen years.