The tests were performed in the presence and absence of a rat-liver homogenate activation system (S.9). In the absence of metabolic activation, 0.1 ml of a solution of the test compound and approximately 10(sub 8) bacteria were added to 2 ml of top agar (0,6% agar, 0.6% NaC1, 0.05 mM L-histidine, 0.05 nM biotin), The solution was mixed and poured on the surface of a Davis minimal agar plate. The metabolic activation system involved the addition of 0,S ml of 3,9 mixture to the chemical-top agar solution. The S.9 mix contains per ml: 0.3 ml of the 9,000 X g supernatant of honogenized rat liver, 8 mM MgC12, 33 mM KC1, 5 mM glucose-6-phosphate, 4mM NADP and 100 mM sodium phosphate (pH 7.4), This mixture was added directly to the top agar immediately before it was poured over the minimal agar plate. Prior to testing for mutagenicity, the compound was tested for toxicity to the tester strains.