OBJECTIVE: This randomized controlled clinical trial investigated the effects of mindfulness meditation on chronic pain. DESIGN: A total of 109 patients with nonspecific chronic pain were randomized to either a standardized mindfulness meditation program (mindfulness-based stress reduction [MBSR]) or to a wait list control. METHODS: Pain, physical function, mental function, pain acceptance, and health-related quality of life were measured. The SF36 vitality scale was chosen as the primary outcome measure; the primary end point was after completing the MBSR course. Within a 2.5-year period, 43 of the 109 randomized patients completed the mindfulness program, while 47 remained in the control group. Data were compared at three time points: at baseline, after completion of the course/waiting period, and at the 6-month follow-up. RESULTS: Significant effect (Cohen's d = 0.39) was found on the primary outcome measure, the SF36 vitality scale. On the secondary variables, significant medium to large size effects (Cohen's d = 0.37-0.71) were found for lower general anxiety and depression, better mental quality of life (psychological well-being), feeling in control of the pain, and higher pain acceptance. Small (nonsignificant) effect sizes were found for pain measures. There were no significant differences in the measures just after the intervention vs the 6-month follow-up. CONCLUSION: A standardized mindfulness program (MBSR) contributes positively to pain management and can exert clinically relevant effects on several important dimensions in patients with long-lasting chronic pain.