A performance audit of the U.S. Geological Survey (USGS), Energy Resource Program (ERP) Inorganic Geochemistry Laboratory (IGL) was conducted between August, 2003 and October, 2005. The goals were to ensure that a high level of analytical performance was maintained and identify any areas that could be enhanced. The audit was subdivided into three phases. Phase 1 was a preliminary assessment of current performance based on recent performance on CANSPEX samples. IGL performance was also compared to laboratories world-wide with similar scope. Phase 2 consisted of the implementation of the recommended changes made in Phase 1. Phase 3 of the audit consisted of a reassessment effort to evaluate the effectiveness of the recommendations made in the Phase 1 and an on-site audit of the laboratory facilities. Phases 1 and 3 required summary reports that are included in Appendices A and B of this report. The audit found that the IGL was one of the top two laboratories compared for trace element analyses. Several recommendations to enhance performance on major and minor elemental parameters were made and implemented. Demonstrated performance improvements as a result of the recommended changes were documented. Several initiatives to sustain the performance improvements gained from the audit have been implemented.