The authors propose a direct method for enzyme-histochemical demonstration of myosin-adenosintriphosphatase, through lead ions and optimal pH = 9.4. They have succeeded in developing a stable complex between tris(hydroxymethyl)aminomethan and lead(II)citrate, as result of which, at the alcaline pH of the enzyme reaction a direct precipitation of the liberated phosphate takes place in the form of lead phosphate. This one-step method for histochemical demonstration of the enzyme makes possible well reproducible results as an enzyme marker of muscle fibres type II in the differentiation of the type of muscle fibre and the evaluation of the sceletal musculature in general. Because of this, the reaction may be applied with success in clinical pathology for the diagnosis of the degenerative muscular diseases of primary or secondary origin.