PolyGlycopleX (PGX), a novel dietary fiber, produces no mutagenic effects in bacterial tester strains Salmonella typhimurium TA 98, TA 100, TA 1535, and TA 1537 and Escherichia coli WP2 uvrA at concentrations of 0.316, 1.00, 3.16, 10.0, 31.6, and 100 μg/plate. No biologically relevant increases in revertant colonies of any of the 5 strains are observed at any concentration; however, a reduction at 100 μg/plate in TA 1537 is noted. PGX, analyzed for polychromatic erythrocyte micronuclei induction in mice following a single 1×, 0.5×, and 0.2× maximum tolerable dose intraperitoneal treatment, produces no biologically relevant increase in any dose group. Males at 1× maximum tolerable dose show a reduction of micronuclei-containing cells. High-dose animals show signs of systemic toxicity, including a reduction of spontaneous activity, rough fur, palpebral closure, prone position, and constricted abdomen. These genotoxicity studies show PGX to be nonmutagenic in both the Ames bacterial reverse mutation assay and the mammalian erythrocyte micronucleus test.