Five and 15 days after T. cruzi infection, staphylococcal protein A was injected into a connective tissue air pouch of mice and the migration of polymorphonuclear leukocytes into the area was monitored. The PMN leukocyte response of 15-day infected mice was lower than that of uninfected mice (P less than 0.001): The 15-day infected mice also showed a lower PMN leukocyte response when compared to 5-day infected mice (P less than 0.001). These data suggest that the chemotaxis defect developed gradually during the acute phase of infection.