This study examines the psychosocial benefits of Internet community group participation for women with breast cancer. A longitudinal content analysis of more than 33,200 postings from an online breast cancer bulletin board, and thematic analysis of the “life stories” of 100 women randomly selected from the bulletin board, was conducted. Psychosocial benefits included: receiving/giving information; receiving/giving social support; affect toward the discussion board, optimism toward breast cancer, increased skill or ability to cope with the disease, improved mood, decreased psychological distress, and strategies to manage stress. Over time, a positive shift was shown in women's affect toward the breast cancer and online community, and a positive correlation was found between amount of participation and psychosocial well-being.