The use of water for medical treatment is probably as old as mankind. Until the middle of the last century, spa treatment, including hydrotherapy and balneotherapy, remained popular but went into decline especially in the Anglo-Saxon world with the development of effective analgesics. However, no analgesic, regardless of its potency, is capable of eliminating pain, and reports of life-threatening adverse reactions to the use of these drugs led to renewed interest in spa therapy. Because of methodologic difficulties and lack of research funding, the effects of 'water treatments' in the relief of pain have rarely been subjected to rigorous assessment by randomised, controlled trials. It is our opinion that the three therapeutic modalities must be considered separately, and this was done in the present paper. In addition, we review the research on the mechanism of action and cost effectiveness of such treatments and examine what research might be useful in the future.