The aim of this study was to estimate the level of scientific evidence contributed by randomized clinical trials in rheumatologic indication of spa therapy. A literature search was made of computer data banks, with analysis of 20 randomized hydrotherapy trials. On the 20 identified randomized hydrotherapy trials, four were carried out double-blind; nine included a comparison of inter-groups evolution. The indications assessed are chronic low back pain, osteoarthritis of the knee and hip joints, osteoarthritis of fingers, fibromyalgia, rheumatoid arthritis and psoriasis arthritis. The results suggest durable, persisting improvement several months after balneological care, in accordance with the following evaluation criteria: pain, handicap, quality of life, consumption of analgesics and of nonsteroidal anti-inflammatory drugs (NSAIDs). It was concluded that randomized evaluations, demonstrating a beneficial and prolonged clinical effect of balneologic treatments, exist in respect of the main indications for rheumatologic hydrotherapy. These results acknowledge the medical help given by hydrotherapy within the aforesaid parameters, to which may be added a reduction of the adverse gastrointestinal events of NSAIDs. Evaluation needs to be continued to clarify the medical benefit offered by rheumatologic hydrotherapy.