The role for neutrophils in the resolution of primary and secondary infection with Listeria monocytogenes was studied, The results show that although control mice started to clear Listeria from their spleens and livers between days 2 and 4 of sublethal primary infection and eradicated bacteria in 2 weeks, mice given a specific granulocyte-depleting antibody (RB6-8C5) on days 4 or 6 of infection developed lethal listeriosis. Likewise, treatment of immunized mice with RB6-8C5 monoclonal antibody abolished their acquired ability to resolve a lethal challenge infection. The results demonstrate that neutrophils are necessary for the resolution of secondary and primary Listeria infection.