A method for measuring the total lactate dehydrogenase activity has been developed on the basis of Warburg's optic test with a photoelectrocolorimeter, making use of lactate as a substrate. The results are calculated from the mean molar coefficient of light absorption. The coefficient of variations of the method is 7.7%. The results obtained with the use of a spectrophotometer and photoelectrocolorimeter have been in good correlation. The described technique is recommended as a method of choice.