The current studyRose (2002) and Rose et al. (2007) have urged the continued study of this integrative construct, which lies at the juncture of self-disclosure and rumination, given its’ promise to enhance our understanding of the developmental course of selfdisclosure, friendship quality, coping responses, and psychological well-being. Unfortunately, her call has been neglected. Insummary, we seek to replicate prior studies using a middle adolescent sample, expecting that: adolescent girls will report higher levels of co-rumination relative to boys, co-rumination will concurrently be associated with higher levels of internalizing symptoms, and co-rumination will partially explain gender differences in internalizing problems. To extend knowledge of co-rumination in new directions, we explored several additional questions: (1) is co-rumination associated with externalizing behaviors? (2) is co-rumination associated with peer acceptance and peer network size? (3) to what extent is co-rumination associated with individual coping efforts? (4) does co-rumination predict unique variance in outcomes?