The thermal water of Vetriolo in Trentino, Italy (VW) has been known over 150 years for its therapeutic properties in the treatment of osteoarthritis (OA). This is a highly mineralized water, strongly acidic sulfate, rich in calcium, magnesium and iron and used for balneotherapy after dilution. The aim of our study was to investigate the possible in vitro effects of the VW in human OA chondrocytes cultivated in the presence or in the absence of Interleukin-1 beta (IL-1beta). OA chondrocytes were cultivated in Deionized Water (DW) (DW-DMEM, controls), or in one of three different VW-DMEM media, in which DW had been totally (100 percent) or in part (25 or 50 percent) substituted with VW. All samples were analyzed before and after treatment with IL-1beta at a concentration of 5 ng/ml. After 48 h, we evaluated the cell viability, the release of nitric oxide (NO) in culture medium, the inducible nitric oxide synthase (iNOS) expression, and the percentage of apoptosis and necrosis. Finally, we carried out a morphological assessment using a transmission electron microscope (TEM). Our data showed that VW alone at 25 or 50 percent concentration did not affect the viability of cultured OA chondrocytes, and determined a significant survival recovery rate in cultures stimulated with IL-1beta. On the contrary, the VW alone at 100 percent of concentration reduced, in a significant (P less than 0.05) manner, the cells viability. NO levels were low both in DW-DMEM cultures and in those reconstituted with 25 or 50 percent of VW, and were significantly (P less than 0.05) increased in cultures with 100 percent of VW. VW at 25 or 50 percent concentration significantly (P less than 0.001) reduced the NO production induced by IL-1beta. The data of the NO levels were confirmed by the immunocytochemistry assay for iNOS. Our experiments confirmed the pro-apoptotic effect of IL-1beta and demonstrated a protective effect of VW at 25 or 50 percent concentration. These findings were confirmed by TEM. In conclusion, our study demonstrated that VW alone at 25 or 50 percent concentration modifies neither morphology nor NO production and neither iNOS expression nor apoptosis, but it inhibits the negative effects of IL-1beta in chondrocytes cultures.