Several observations have demonstrated the importance of T-cell-mediated mechanisms in experimental Chagas' disease. In previous studies, we have shown that mice acutely infected by Trypanosoma cruzi develop a progressive thymic atrophy with severe alterations in the lymphoid compartment. In this report we performed a kinetic analysis of the murine thymic lymphocytes comparing acute and chronic phases of infection. At the chronic phase, we observed that total thymocyte numbers returned to age-matched control values. Additionally, the decrease in the percentage of CD4+CD8+, in parallel with an increase of CD4+CD8-, CD4-CD8+, CD3high, TcR alpha beta and TcR gamma delta cells detected in the acute infection, was also restored in chronically infected mice. This thymocyte recovering is probably linked to the increase in the percentage of thymocyte precursors, such as CD4lowCD8- and CD4-CD8low cells, together with the increase in the number of IL-2R+ and cycling cells, appearing in the late stages of acute infection.