Ten cross-bred calves (Holstein x Zebu) were infected with helmintics larvae. Three female calves had 4 to 5 months and 7 male calves, 4 to 7 months of age. Of the larvae given to them, 1720 were Cooperia sp., 1560 Oesophagostomum sp. and 720 were Haemonchus sp. This experiment was projected to study the changes in serum proteins, namely the total one and particulary its fractions: Albumin and the alpha 1, alpha 2, beta and gamma globulins. Before infection and after it 54 days, with 6 day intervals, the animals were bled for making the respective examination. The results were as follows low percentage of protein and albumin, alpha 1, alpha 2, beta e gamma globulins, as well as the ratio albumin/globulin were practically unchanged. The data were statistilly analysed.