Summary.Determinations of the pyruvate and lactate content of capillary blood during the steady state of heavy muscular work showed, that both substances are found in increasing amounts with increasing severity of work. At cessation of work the lactate concentration immediately began to decrease, whereas the pyruvate concentration showed a further increase with its maximum 3–5 minutes after cessation of work, before it began to decline.The ratio lactate pyruvate consequently has different values during pyruvate work and at different times after work.It is assumed that the increased amount of pyruvate found in the blood during and after work is formed by the oxidative elimination of the lactic acid,We are greatly indebted to dr JENS HALD of the Biological Laboratories ofMedicinalco Ltd.who kindly provided us with hard to get chemicals and valuable advic