Eleven metals were examined for their potential to induce forward mutations at the thymidine kinase locus in L5178Y mouse lymphoma cells. The materials tested included AICI3, CdSO4, HgCI2, K2CrO4, K2Cr2O7, MgCI2, MnCI2, NaAsO2, Na2HAsO4, NaCI, and Pb(NO3)2. Strong positive responses at survivals greater than 10% were observed with CdSO4, K2CrO4, K2Cr2O7, and MnCI2. Weak positive responses, yielding 2‐ to 3‐fold increases in mutation frequency above the solvent control at greater than 10% survival, were seen with HgCI2, NaAsO2, No2HAsO4, and Pb(NO3)2. Negative responses were obtained with MgCI2, NaCI, and AICI3.