The 16th edition of the Official Methods of Analysis, 4th Revision, current through March 1998, includes over 222 new and 505 revised methods not included in the 15th edition. Many of the existing methods have been significantly revised since the 15th edition to extend their applicability or to improve their accuracy or both. Additional methods have been declared surplus. These actions represent the Association’s response to the AOAC mandate to keep pace with the practical needs of regulatory, industry, and research chemists and microbiologists.