Objective To introduce the basic information about mad cow disease and the current status of safety control of medical devices derived from mammalian animal tissues. Methods Literature concernedwas reviewed intensively. Results Mad cow disease, also knownas bovine spongiform encephacitis (BSE)， is generally considered from the samesource of Scrapie, and they are caused by the same kind of sponginess brain tissue pathological changes. Mad cow disease is caused by the misfolding of a small protein called Prion. This disease has the character of slowly breaking down the central neuron system of animals. Conclusion Further researches can provide evaluation for safety considerations of medical devices deriving from animal.