Quality assurance and quality control is the foundation of any diagnostic test. The two laboratories in the United States that use HPLC to quantitate endophyte toxins in tall fescue (Festuca arundinacea) and perennial ryegrass (Lolium perenne) are Oregon State University (OSU) and University of Missouri (MU). Japan, the major importer of grass straw has six new laboratories that will test agricultural imports for endophyte toxins. A quality assurance program was set up between the Japanese Ministry of Agriculture and the State of Oregon. The latter includes both OSU and the MU. All units are using an accurate crystalline standard and have exchanged "check" samples among themselves. To date OSU and MU have values that differ by 10%. OSU has identified a contaminating and coeluting peak as the cause of the differences. Both laboratories are changing to a Gemini column to rectify the differences. Japanese laboratories are in the process of evaluating their split check samples. Keywords: quality assurance, quality control, endophyte, tall fescue, perennial ryegrass