This study focused on developmental changes in friendships, and examined the relationship of support reciprocity and stress responses, taking specific account of Austin andWalster’s (1974, 1975) concepts of person-specific equity and equity with the world. The participants were 127 elementary, 216 junior high, and 262 high school students in Japan. They provided names of their three close friends and were asked about the exchange of support with each friend, in addition to responding to a stress response scale. The results indicated that the support reciprocity of the best friend and the second best friend, and the total support reciprocity of all the three close friends had a significant quadratic relationship to stress responses among the high school students