The cytotoxicity of povidone-iodine in Repithel, Betaisodona ointment and Betaisodona solution was investigated using CHO-K1 cells. To estimate the vitality of test cells after 30 min contact time using vital dye neutral red, the following IC(50) were determined: 16-18% Repithel, 8-9% Betaisodona ointment and 1.8-2% Betaisodona solution; using MTT for detecting vitality, the IC(50) were: 5-10% Repithel, 1.3-2.5% Betaisodona ointment and 0.6-1.3% Betaisodona solution. Therefore, the first attack of the antiseptic agent iodine to mammalian cells is carried out on enzymes, perhaps by oxidation, followed by membrane attack. Murine fibroblasts were used to compare the cytotoxic impact of povidone-iodine with those of chlorhexidine digluconate (CHex), octenidine dihydrochloride (Oct) and polyhexamethylene biguanide (PHMB). On the base of molecular concentration, povidone-iodine is more than 20 times better tolerated by L929 cells than CHex, Oct or PHMB. Moreover, after 30 min contact of L929 cells with povidone-iodine, there is a temporarily cytotoxic reaction, which leads after 24 h culture to an unexpected revitalisation of murine fibroblasts. This phenomenon was not detected using CHex, Oct or PHMB. Povidone-iodine seems to be the most tolerated antiseptic in comparison with CHex, Oct or PHMB.