Balb/c mice were infected intraperitoneally with protoscoleces of Echinococcus granulosus. After 15 months of infection, and by means of flow cytometry, the expression of T-cell markers CD3, CD4, and CD8 on T cells from peripheral blood, spleen, and thymus was analyzed and compared with that of age-matched controls. Infected mice had higher percentages of CD3+, and CD4+ cells in peripheral blood, and higher percentages of CD8+ cells in the spleen, when compared with control mice. CD4+ and CD8+ cells in peripheral blood and CD8+ cells in thymus also showed higher percentages of expression of interleukin-2 receptor. The results infer a role for interleukin-2 in experimental secondary echinococcosis.