There remains much controversy surrounding the role of Th2 cytokines, such as interleukin-4 (IL-4), in tuberculosis infection. Here we demonstrate that anti-IL-4 antibody, administered as a pulse during the early or late stages of murine infection, can provide significant reductions in the bacterial burden. The fact that substantial benefit can be achieved when treatment is administered during established infection strengthens the view that clinical interventions aimed at suppressing the IL-4 component of the host immune response seen in tuberculosis patients may be beneficial.