Twenty-eight Brazilians from an area in which Wuchereria bancrofti is endemic were classified as asymptomatic microfilaremic or having clinical filariasis with active infection or without current active infection. Total accumulation of antigen-specific interleukin (IL)-4 and IL-5 in 48 h peripheral blood mononuclear cell supernatants was not significantly different between groups. However, when cytokine kinetics were examined, responses segregated according to infection status. Sustained production of IL-4 and IL-5 beyond the first 24 h of stimulation and production of interferon-gamma were seen only in the group with clinical filariasis without active infection. CD8 T cells were the major source of IL-5 production in this group, while CD8 production of IL-5 was undetectable in any subject with active infection (asymptomatic microfilaremic or with clinical filariasis and active infection). These findings indicate that active infection, rather than clinical status, is most closely associated with cytokine patterns in lymphatic filariasis.