Independent determinations of the acute oral LD 50 in 200- to 300-g albino rats were made of four commercial chemical products by six testing laboratories. The products tested were sodium bicarbonate, sodium alkylbenzene sulfonate, a granular household detergent, and a liquid household detergent. Interlaboratory differences of two- to threefold were observed in the LD 50 values, which could be accounted for in part by differences in dose concentration and vehicle. In other cases differences were observed that could not be attributed to these or other known factors.