The data of 33 randomized controlled trials suggest that chronic pain of patients with chronic low back pain, knee osteo-arthritis, fibromyalgia is significantly improved by balneotherapy and significantly better improved than by control treatments. For chronic low back pain (10 RCT, 1192 patients) pain was better improved in balneotherapy group and the weighted mean of the differential improvement was 19.66 (95 % CI: 16.6 ; 22.8) and the effect size was 1.1 (95 %CI: 0.82 ; 1.38) favouring balneotherapy. For knee osteo-arthritis pain (17 RCT, 1428 patients) pain was better improved in balneotherapy group and the weighted mean of the differential improvement was 13.24 (95 % CI: 5.52 ; 20.96) and the effect size was 0.72 (95 %CI: 0.51 ; 0.93) favouring balneotherapy. For fibromyalgia (6 RCT, 398 patients) pain was better improved in balneotherapy group and the weighted mean of the differential improvement was 19.32 (95 % CI: 10.62 ; 29.2) and the effect size was 0.79 (95 %CI: 0.27 ; 1.31) favouring balneotherapy. Mineral waters and healing muds appear to have a more powerful analgesic action: 13 RCT (701) patients) compared mineral water bathing to tap water bathing or peloid application to hot-apcks or neutral muds application : the effect size was 0.75 (95 % CI :0.71 ; 0.79) favouring balneotherapy. Balneotherapy is a safe treatment as only 1 % of the patients receiving balneotherapy had to interrupt the treatment. However several methodological biases were observed in many trials, mainly a lack of statistical power due to a limited enrolment of patients, an insufficient duration of follow-up, an inhomogeneity of treatments. The clinical benefit has to be confirmed by stronger data of evidence but these data are sufficient to perform a more complete scientific analysis (meta-analysis) ; but further clinical investigations with a better methodological quality remain necessary.