The changes were followed up that take place in the activity of the more important serum enzymes, such as glutamate oxalacetate transaminase, glutamate pyruvate transaminase, serum dehydrogenase, malate dehydrogenase, lactate dehydrogenase, creatine phosphokinase, and alkaline phosphatase, as well as aldolase in the development of the experimental infection with various doses of Taenia ovis eggs in lambs. Used were 14 two-month-old lambs divided into test groups of 4 animals each and a control group of two lambs. In the lambs of three of the test groups infected with 4000, 7000, and 30 000 T. ovis eggs, respectively, no signs were observed of enhanced serum enzyme activity up to the 35th day following infection. Later on there was a drop of the activity of these enzymes however, with the exception of alkaline phosphatase the values of all studied serum enzymes remained higher than the normal ones up to the end of the experiment.