The text article, Sodium dimethyldithiocarbamate, was tested in the chromosome aberration assay using Chinese hamster ovary cells. The assay was conducted both in the absence and presence of an Aroclor-induced S-9 activation system at dose levels of 3, 1, 0.3, 0.1 nl/ml and 20, 10, 3, 1 nl/ml. respectively. A delayed harvest was also carried out at 3 and 1 nl/ml in the absence of S-9 and at 20 nl/ml in the presence of S-9 because of cell cycle delay at this dose level. A statistically significant increase in structural chromosome aberrations was observed at the highest dose tested in the presence of S-9. No increase was observed in the nonactivated study. Sodium dimethylidithiocarbamate was conducted to be suspect in the CHO chromosome aberration assay in the presence of S-9 and negative in the absence of S-9.