OBJECTIVE: To evaluate the association between complementary and alternative medicine (CAM) use, satisfaction with treatment, and patient-reported outcomes after treatment. METHODS: The Prostate CAncer Therapy Selection Study prospectively surveyed patients newly diagnosed with localized prostate cancer about their treatment decision-making process and outcomes. The Prostate CAncer Therapy Selection Study recruited patients from 3 geographic areas through hospital-based urology clinics and community urology practices. RESULTS: More than 700 patients completed the baseline and follow-up surveys. More than 50% of respondents reported using CAM; this decreased to 39% if prayer was excluded as a type of CAM. On multivariate analysis, factors related to communication with the treating physician, but not CAM use, were associated with treatment satisfaction. The likelihood of stability or improvement in urinary, bowel, and sexual function at 6 months was related to the choice of primary therapy but was unrelated to CAM use. CONCLUSION: In the present prospective observational study, CAM use was highly prevalent but unrelated to treatment satisfaction or changes in functional status. The effect of CAM on these endpoints remains to be established in comparative effectiveness studies.