<jats:title>Abstract</jats:title><jats:p>Metallic biomaterials implanted in a human body may corrode and wear, releasing metal ions and debris which may induce adverse reactions such as inflammation, allergy, neoplastic formation, developmental malformation, etc. Mutagenicity is a very fundamental and important toxicity related to carcinogenicity and reproductive/developmental toxicity because the damages to genes or DNA can be a cause of carcinogenesis and developmental abnormalities. However, available mutagenic data on metallic ions and compounds are restricted to the number of elements. Therefore, to obtain the systematic data necessary for metal ion mutagenicity, 41 metal salts encompassing 36 metals and 5 metallic elements tested with different valences, were evaluated on their mutagenicity by a microbial test, the <jats:italic>umu</jats:italic> test. As a result, K<jats:sub>2</jats:sub>Cr<jats:sub>2</jats:sub>O<jats:sub>7</jats:sub>, RhCl<jats:sub>3</jats:sub>, IrCl<jats:sub>4</jats:sub>, and MgCl<jats:sub>2</jats:sub> are positive without metabolic activation. Concentrations having the maximum mutagenic effect (<jats:italic>C</jats:italic><jats:sub>max</jats:sub>) are 9.65 × 10<jats:sup>−5</jats:sup>, 1.00 × 10<jats:sup>−4</jats:sup>, 3.11 × 10<jats:sup>−3</jats:sup>, 4.12 × 10<jats:sup>−3</jats:sup> mol · L<jats:sup>−1</jats:sup>, respectively. CuCl<jats:sub>2</jats:sub>, VCl<jats:sub>3</jats:sub>, CuCl, RhCl<jats:sub>3</jats:sub>, K<jats:sub>2</jats:sub>Cr<jats:sub>2</jats:sub>O<jats:sub>7</jats:sub>, and IrCl<jats:sub>4</jats:sub> are positive with metabolic activation by S‐9 mix with <jats:italic>C</jats:italic><jats:sub>max</jats:sub> of 1.60 × 10<jats:sup>−5</jats:sup>, 3.91 × 10<jats:sup>−5</jats:sup>, 1.57 × 10<jats:sup>−4</jats:sup>, 2.00 × 10<jats:sup>−4</jats:sup>, 3.86 × 10<jats:sup>−4</jats:sup>, 1.56 × 10<jats:sup>−2</jats:sup> mol · L<jats:sup>−1</jats:sup>, respectively. Thirty‐five metal salts were negative for tests performed both with and without metabolic activation, whereas it was impossible to evaluate the mutagenicity of MoCl<jats:sub>5</jats:sub> and ZrCl<jats:sub>4</jats:sub> by the <jats:italic>umu</jats:italic> test because of their colorimetric reaction to testing reagents. © 2001 Wiley Periodicals, Inc. J Biomed Mater Res 59: 176–183, 2002</jats:p>