All laboratories conducting tests for the LTPP program were required to be accredited by the American Association of State Highway and Transportation Officials (AASHTO) Accreditation Program (AAP). AAP includes site inspections of equipment and procedures, and participation in applicable proficiency sample testing. Since a few critical LTPP tests were not addressed fully by the AAP, supplemental testing was conducted. The asphalt concrete synthetic reference sample program and the asphalt concrete core proficiency sample program were among the supplemental programs approved for implementation. Worksheets, supporting data, analyses, final comments, and conclusions are presented. A complete set of proficiency sample statements in AASHTO/ASTM format are provided.