Contact sensitization capacity of four metal salts, nickel sulphate (NiSO 4), potassium dichromate (K 2Cr 2O 7), titanium chloride (TiCl 4) and zirconium chloride (ZrCl 4), was evaluated using guinea-pigs and mice. In the guinea-pig sensitization tests, we set up an injection concentration to 1% for all chemicals, and changed the challenge concentration. Guinea-pigs were sensitized with NiSO 4, K 2Cr 2O 7 and TiCl 4. Among the test metal salts, K 2Cr 2O 7 showed the highest sensitization rate and strongest skin reactions. ZrCl 4 did not cause any sensitization responses under our experimental conditions. Minimum challenge concentration to cause a skin response was <0.25% for K 2Cr 2O 7, 0.5% for NiSO 4 and 2% for TiCl 4, respectively. A sensitive mouse lymph node assay (SLNA) also determined NiSO 4 and K 2Cr 2O 7 as a sensitizer. In the SLNA, TiCl 4 caused mild lymph node responses, but was classified as a non-sensitizer as well as ZrCl 4. Considering these results, the order of sensitization potential was K 2Cr 2O 7 > NiSO 4 > TiCl 4 > ZrCl 4. NiSO 4- and K 2Cr 2O 7-sensitized animals did not show any reactions to ZrCl 4 and TiCl 4. No cross-reaction among these metal salts was found.