Thermal therapy is used worldwide in the treatment of psoriasis but few controlled studies have evaluated its efficacy and safety. We studied the efficacy and safety of balneotherapy compared to photobalneotherapy performed at Comano spa in Trentino, Italy, in chronic plaque psoriasis in a prospective, nonrandomized, open study. Three hundred adult patients with mild to severe chronic plaque psoriasis were assigned to either balneotherapy or photobalneotherapy with daily narrow-band ultraviolet B for a mean period of 1 or 2 weeks, reflecting the times that most patients can dedicate to thermal therapy. Patients were evaluated at baseline and end of treatment for psoriasis area and severity index (PASI) and body surface area; self-administered PASI (SAPASI) and Skindex-29 were evaluated at the same times, and also at 4 months by a mailed questionnaire. One-week balneotherapy or photobalneotherapy resulted in a significant reduction in PASI score (11.54% +/- 2.76 and 12.76% +/- 3.79, respectively; mean +/- standard deviation; p < 0.001). Two-week therapy induced a greater response with photobalneotherapy than with balneotherapy alone, with PASI reduction of 19.8% +/- 24.5 and 13.5% +/- 23.1 (p < 0.005), respectively. These results were confirmed by SAPASI and Skindex-29 evaluation. The therapy was well tolerated. Skin improvement was mostly lost after 4 months. Short-term balneotherapy and photobalneotherapy could thus be offered to patients willing to temporarily discontinue pharmacologic therapy or as adjuvant therapy.