The National Assessment Governing Board used a new method to set achievement level standards on the 2005 Grade 12 NAEP Math test. In this article, we summarize our independent evaluation of the process used to set these standards. The evaluation data included observations of the standard-setting meeting, observations of advisory committee meetings where the results were discussed, review of documentation associated with the standard-setting study, analysis of the standard-setting data, and analysis of other data related to the mathematics proficiency of 2005 Grade 12 students. Our evaluation framework used criteria from the "Standards for Educational and Psychological Testing" (AERA, APA, & NCME 1999) and other suggestions from the literature (e.g., Kane, 1994, 2001). The process was found to have adequate procedural and internal evidence of validity. Using external data to evaluate the standards provided more equivocal results. In considering all evidence and data reviewed, we concluded the process used to set achievement level standards on the 2005 Grade 12 NAEP Math test was sound and the standards set are valid for the purpose of reporting achievement level results on this test. Recommendations for future NAEP standard-setting studies are provided. (Contains 7 footnotes, 3 tables and 1 figure.)