This study investigated the profiles of IFN-gamma and its regulatory cytokines (IL-12, IL-18 and IL-10) in response to a purified protein derivative (PPD) antigen in peripheral blood mononuclear cells (PBMC) from 18 HIV-negative patients with multidrug-resistant tuberculosis (MDRTB), and compared them with those from 19 healthy tuberculin reactors (HTR). ELISA results showed that following stimulation with PPD, IFN-gamma production was significantly reduced, whereas production of both IL-18 and IL-10 was significantly elevated in MDRTB patients compared with HTR. Three out of 18 patients with MDRTB of greater than 4 years duration showed significantly elevated IL-12 p70 production, induced by in vitro PPD stimulation of their PBMC, when compared with data from HTR. However, when taken as a group, MDRTB patients were similar to HTR in their IL-12 p70-producing capacity. IL-12 p70 protein paralleled IL-12 p40 protein expression. In addition, the production of IL-12 p40 was significantly correlated with IL-10 in all patients, but was not correlated with IFN-gamma. Neutralization of IL-10 increased IL-12 p40 about twofold, but did not significantly alter IFN-gamma induction in MDRTB. IFN-gamma in MDRTB was highly correlated with lymphoproliferation and CD4 counts, but was not correlated with IL-12, IL-18 or IL-10 production. Our findings suggest that patients with MDRTB have dysregulated IL-12, IL-18 and IL-10 production during Mycobacterium tuberculosis infection, and the cytokine profiles are similar to those in patients with drug-sensitive advanced TB previously reported in the literature. In addition, IL-10 may not have a dominant role in defective IFN-gamma production in patients with MDRTB.