Regulatory T cells, which stimulate or inhibit the effector functions of distinct T cell subsets, are critical in the control of the immune response. We investigated the effect of TGF-beta and IL-10 on T cell subsets according to the Th1/Th2 immune status. Sixty-two patients with asthma and 38 patients with pulmonary tuberculosis were included. Allergy skin tests, tuberculin tests, and chest radiography were performed. The levels of circulating IL-4, IFN-gamma, TGF-beta1, and IL-10 were measured using ELISA. The level of TGF-beta1 was higher in patients with asthma than in those with tuberculosis, but the IL-10 levels were the same between the asthma and tuberculosis groups. Atopy was unrelated to the tuberculin response. The IFN-gamma level was correlated with the IL-10 level, and the level of IL-4 was unrelated to the IL-10 or TGF-beta1 level. The level of IL-10 was higher in the negative tuberculin reactors than in the positive tuberculin reactors among patients with asthma, and TGF-beta1 was higher in the positive tuberculin reactors than in the negative tuberculin reactors among patients with tuberculosis. These results demonstrate that the regulatory effects of circulating TGF-beta and IL-10 on T cell cytokines may be different between Th2-type asthma and Th1 tuberculosis.