To determine the effect of measles virus infection on cytokine production in children from sub-Saharan Africa, temporal changes in cytokine production in vivo were analyzed and the T cell sources of type 1 and type 2 cytokines were identified in Zambian children with measles. The immune response during measles involved early type 1 responses, with production of interferon-gamma by CD8(+) T cells and of interleukin (IL)-2 by CD4(+) T cells. Subsequently, more-prolonged increases were observed in the type 2 cytokines IL-4 and IL-13, both produced by CD4(+) T cells. IL-5 was regulated differently from IL-4 and IL-13: levels were low compared with levels in control children and were reflected in lower eosinophil counts during measles. Immunoglobulin E was lower in children with measles, despite high levels of IL-4 and IL-13. Plasma levels of IL-10 were elevated for weeks, potentially contributing to impaired cellular immunity and depressed hypersensitivity responses following measles.