Background: Internet-based methods for provision of psychological support and intervention to cancer survivors hold promise for increasing the public impact of such treatments. Purpose: The goal of this controlled pilot study was to examine the effect and potential mechanisms of action of a self-guided, Internet-based coping-skills training group on quality of life outcomes in women with early-stage breast cancer. Methods: Sixty-two women completed baseline evaluations and were randomized into either a small online coping group or a waiting-list control condition. Results: No main effects for treatment were observed at the 12-week follow up. However, there was a significant interaction between baseline self-reported health status and treatment, such that women with poorer self-perceived health status showed greater improvement in perceived health over time when assigned to the treatment condition. Linguistic analyses revealed that positive changes across quality of life variables were associated with greater expression of negative emotions such as sadness and anxiety, greater cognitive processing, and lower expression of health-related concerns. Conclusions: These results demonstrate the potential efficacy of self-guided Internet coping groups while highlighting the limitations of such groups. © 2005 by The Society of Behavioral Medicine.