We have created a mindfulness approach to treat patients who experience multiple, persistent, and disabling physical symptoms that cannot be explained by a well-defined medical or surgical condition. Randomized controlled trials in this area are few, and research is hampered by the lack of clear definitions. Bodily distress syndrome (BDS) or bodily stress is an empirically defined definition unifying various conditions such as fibromyalgia, chronic fatigue syndrome, and somatization disorder. In the present PhD, we explored whether patients suffering from BDS may be committed to mental training in the form of mindfulness therapy, which is a mindfulness program specifically targeted patients suffering from BDS. The theoretical model for including mindfulness training in the treatment of BDS is based on identified neurobiological impairments in these patients and the neurobiological improvements that mindfulness training may offer. BDS is a major public health issue possibly associated with the pathology of the immuno-endocrine and autonomic nervous system. BDS patients are often stigmatized, and effective treatment is rarely delivered, which leaves these patients isolated, left by themselves, vulnerable to potentially harming medical and/or alternative treatments. Accordingly, there is a need for non-harming practical tools that patients can learn to master so that they can improve the ability to take responsibility for their own health and wellbeing. Mindfulness-Based Stress Reduction (MBSR) is a group program that employs mindfulness practice to alleviate suffering associated with physical, psychosomatic, and psychiatric disorders. Mindfulness-Based Cognitive Therapy (MBCT) is designed to prevent depressive relapse. Paper I and II present systematic literature reviews only of randomized controlled trials on MBSR and MBCT. The effect of MBSR has been explored on fibromyalgia in three studies, none of them showed convincing results, but gave some indications as to improvement. The reviews recommended MBSR as a useful method for improving mental health; however, lack of long-term follow-up and active control groups are limitations in most studies. MBCT was recommended as a tool for preventing depressive relapse in recovered, recurrently depressed patients, but the implication of MBSR and MBCT is problematic, especially due to the lack of well educated mindfulness teachers. We combined MBSR with cognitive behavioral therapy, CBT, specifically targeted BDS. Paper III provides original data from 119 patients enrolled in a randomized clinical trial, mindfulness therapy for BDS. The randomized controlled trial indicates that BDS patients are capable of and willing to engage in mindfulness therapy. This thesis showed that mindfulness therapy can safely and successfully engage BDS patients in mindfulness practice. Since individual CBT and psychiatric consultation have previously been found to have positive outcomes for BDS patients, we compared mindfulness therapy to an active control group entitled specialized treatment in which an individual treatment was planned in collaboration between the patient and an MD specialized in BDS, CBT, and psychiatry. Mindfulness therapy was comparable to specialized treatment in improving the quality of life and the symptoms of the patients with BDS at 15-month follow-up. For primary outcome physical health (PCS) at 15-month follow-up, different developments over time for the two treatment groups could not be established (F(3,2674) = 1.51, p = 0.21). However, in the mindfulness therapy group, PCS significant changed at the end of treatment and this change remained at 15-month follow-up, whereas no significantly change was seen in the specialized treatment group until at the 15-month follow-up. In the mindfulness therapy group, 26%; CI: 14-38 reported a marked improvement (> 1 SD) at the end of treatment compared with 10%; CI: 2-18 in the specialized treatment group. This amounts to a statistically significant difference between the groups (OR = 3.21; CI 1.05-9.78, p = 0.04). The results are indicating that mindfulness therapy produced greater and more rapid improvements than specialized treatment. Mindfulness therapy appears to produce improvements within the range of those reported in the STreSS-1 trial, where CBT was compared with enhanced usual care, and no improvements on the SF-36 scale were observed in the enhanced usual care group. This indicates that the changes accomplished with the two treatments mindfulness therapy and specialized treatment reflect real changes attributable to the interventions. The economic effects of mindfulness therapy are evaluated in paper IV by the use of original register data from the 119 enrolled patients and a matched control group of 5,950 individuals. Mindfulness therapy had substantial socioeconomic benefits over specialized treatment. The costs incurred to cover permanent health-related benefits, especially disability pension, were significantly lower in the mindfulness therapy group than in the specialized treatment group over a 15-month follow-up period; 25% from the mindfulness therapy group received disability pension compared with 45% from the specialized treatment group (p = 0.025). The total health care utilization was reduced over time in both groups from the year before inclusion (mean $ 5,325, median $ 2,971) to the year after inclusion (mean $ 3,644, median $ 1,593) (p = 0.0001). There was no difference between the two groups. Five and ten years before their inclusion, the BDS patients were less self-supporting than an age-, gender- and ethnicity-matched population control group; the BDS patients accumulated more weeks of sickness benefit and unemployment. Thus, the included BDS patients may have been ill and in high risk for a social decline five and ten years before they received a proper diagnosis and treatment. In conclusion, the social and economic consequences of BDS are significant and mindfulness therapy may have a potential to significantly improve function, quality of life and symptoms, prevent a social decline, and reduce societal costs.