The aim of the present study was to determine the effect of supplementation with selenium and vitamin E on the hematological parameters of lambs infected experimentally with Haemonchus contortus. Thirty female lambs were distributed into the following groups: group 1, infected animals; group 2, infected and supplemented animals; group 3, controls; group 4, noninfected and supplemented animals. Groups 1 and 2 received 5,000 larvae of H. contortus (L3) orally per animal. In groups 2 and 4, supplementation with 0. 1 mg/kg sodium selenite (1. 67%) and 2,000 IU of vitamin E, administered intramuscularly, was performed on day 0. Blood sampling was performed on days 0, 20, 30, 45, 60, and 80 to determine the hemogram. Eggs per gram of feces (EPG) was quantified on days 0, 20, 45, and 80. In relation to the number of erythrocytes, hematocrit, hemoglobin, total leukocytes, and lymphocytes, principal differences were observed when parasitized groups were compared with the supplemented-only group, where the latter maintained the highest levels. In lambs supplemented with vitamin E and selenium, there was an increase in cellular immune response mediated by neutrophils. © 2010 Springer-Verlag London Limited.