A rich literature exists reinforcing the notion that both perceived and received social support has stress ameliorating and protective benefits both psychologically and physiologically. However, recent literature suggests that excessive dyadic negative problem talk about an issue, a phenomenon labeled co-rumination, may reverse much of the beneficial effects of social support. Healthy young adults participated in a laboratory research study exploring the associations between co-rumination and immune system inflammatory response. Partial correlations indicated a positive association between co-rumination and C-reactive protein and a negative association between co-rumination and interleukin-6 after controlling for stress, anxiety, and temperature. Discussion focuses on the means by which co-rumination may lead to negative health outcomes.