1.1 The purpose and scope of this guide is to present background material and to establish criteria by which protocols and procedures for conducting the L5178Y/TK +/- 3.7.2C mouse lymphoma mutagenicity assay (commonly referred to as the mouse lymphoma assay, (MLA)) can be properly understood and evaluated. These guidelines are also intended to aid researchers and others to gain a better understanding of the critical elements involved with mammalian cell mutagenicity testing. More specifically, this guide is intended to provide for researchers the accomplishment of the following goals:

1.1.1 Provide an understanding of the critical procedures (steps) in the performance of this mammalian cell mutagenicity test.

1.1.2 Provide generalized criteria by which researchers can evaluate if they are properly performing, utilizing, and interpreting this assay.

1.1.3 Provide criteria by which individuals responsible for evaluating MLA data can determine if the experiments have been properly performed and interpreted.

1.1.4 Provide a basis from which new procedures and developments in testing procedures can be evaluated.

1.1.5 Provide an understanding of the types of genetic damage (that is, gene and chromosomal mutation) that may be detected in this mammalian cell mutagenicity test.