Laboratory animal bedding should provide a surface that is hygienic and that fulfils both physical and chemical requirements essential to the health and well being of the animals. It should be chosen in view of its absorbent capacity, its availability and low dust content. Wood appears to be the most suitable raw material for laboratory animal bedding. Of the softwoods, pine and cedar are not usable because of their high resin content of toxic substances for laboratory animal. Scientists demonstrated some changes in microsomal oxidative enzyme activity and other damages in the mouse and rat depending on the bedding. Aspen, birch, fir, and spruce seem to be good sources, as well as corncob and recycled paper. Based on preference testing, the size and the shape might be the major factors in the suitability of bedding particles for laboratory rodent animals. Bedding consisting of large fibers seems to be preferred. Sterilization is recommended. The paper reviews the history and development in criteria of biological evaluation of laboratory animal bedding, with author's opinion about rodent laboratory animal bedding in China.