The concentrations of 27 trace elements in the basalt BIR‐1, as well as in other mafic rock reference materials, have been determined by ICP‐MS, using pure elemental solutions for external calibration and standard additions. Concentrations of rare earth elements in BIR‐1 for the new ICP‐MS data, agree with compiled values, and previous ID‐SSMS results, whereas ICP‐MS data on HFSE's are systematically higher by about 40% to 70% than ID‐SSMS, but are consistent with data generated at other ICP‐