During TB cytokines play a role in host defence. To determine the cytokine pattern during various disease stages of TB, serum levels of IL-12, interferon-gamma (IFN-gamma), IL-4, IL-6 and IL-10 were measured in 81 patients with active TB, 15 patients during therapy and 26 patients after anti-tuberculous therapy as well as in 16 persons who had been in close contact with smear-positive TB and in 17 healthy controls. IFN-gamma was elevated during active TB when compared with healthy controls, declining during and after treatment. IL-12 (p40 and p70) serum levels were not significantly higher in patients with active TB compared with any of the other groups. IL-4 levels were low in all groups. IL-6 and IL-10 serum levels were elevated in patients with active TB and during treatment. In patients with active TB serum levels of IFN-gamma and IL-6 were higher in patients with fever, anorexia and malaise. IL-12 levels were higher in patients with a positive smear. Cytokine levels did not correlate with localization of TB (pulmonary versus extrapulmonary), or skin test positivity. Cytokines directing a Th1 response (IL-12) or a Th2 response (IL-4) were not elevated in sera of this large group of patients with pulmonary and extrapulmonary TB. In patients with active TB, cytokines that were elevated in serum were IFN-gamma, IL-6 and IL-10.