Dietary fiber supplementation can increase the size and nutrient absorption capacities of the small intestine in some mammals, but does this increase the risk of accumulating environmental contaminants? This study addressed this question by feeding mice diets containing various types of fiber at 0 or 100 g/kg (cellulose, lactosucrose, polydextrose, indigestible dextrin, soy polysaccharide, rice bran and chitosan) for 10 wk. During the final 2 wk, the mice were fed retinol and a dose of Arochlor 1254 [polychlorinated biphenyls (PCB)] estimated to be 5% of the median lethal dose. Accumulation was determined using whole blood samples collected on days 1, 3 and 7 as well as eight tissues (whole blood, small and large intestine, liver, gall bladder, mesentery, kidney and brain). Elimination of Arochlor 1254 and retinol was determined using daily collections of feces and urine. The patterns of accumulation and elimination differed between Arochlor 1254 and retinol, among tissues, and among mice fed diets with various amounts and types of fiber. Dietary fiber supplementation did not decrease accumulation of PCB. However, the diet with chitosan increased fecal excretion of Arochlor 1254 compared to the fiber-free diet (P<0.05). The diets with fermentable fiber (polydextrose, indigestible dextrin and soy polysaccharides) increased urinary excretion of PCB compared to the diets with water-insoluble fiber (cellulose, rice bran and chitosan; P<0.05). The most efficacious diets for minimizing accumulation of environmental contaminants and accelerating elimination likely include a combination of soluble and insoluble fiber, but the specific types, proportions and amounts remain to be determined.