................................................................................................................................ 6 INTRODUCTION ..................................................................................................................... 10 MATERIALS ............................................................................................................................ 11 TEST ARTICLE CONTROL ARTICLES INDICATOR CELLS CULTURE MEDIUM METABOLIC ACTIVATION SYSTEM EXPERIMENTAL PROCEDURES ....................................................................................... 14 DOCUMENTATION TEST SYSTEM IDENTIFICATION SOLUBILITY TEST DETERMINATION OF pH PREPARATION OF TEST CULTURES PREP ARA TION OF METABOLIC ACTIVATION SYSTEM PREPARATION OF TEST ARTICLE DOSING SOLUTIONS RANGE FINDING TEST DEFINITIVE CHROMOSOME ABERRATION ASSAY CONFIRMATORY CHROMOSOME ABERRATION ASSAY STATISTICAL ANALYSIS CRITERIA FOR A VALID ASSAy ....................................................................................... 20 EVALUATION OF TEST RESULTS .................................................................................... 20