Bronchial asthma is a chronic inflammatory disorder of the airways. Balancing in Th1 and Th2 response is a target in the treatment. Recent studies show that interleukin-10 (IL-10) has an important role in the regulation of Th2 and allergic responses and its amount was found to decrease in asthmatic patients. This study was to focus on cytokine responses, including interferon-gamma (IFN- gamma), IL-4 and IL-10 in asthmatic children during acute exacerbation compared to stable period. Peripheral blood mononuclear cells (PBMCs) from fourteen asthmatic children during exacerbation and stable phase were stimulated with phytohemagglutinin (PHA) and mite allergen (Der p) for 72 hours. Levels of IFN-gamma, IL-4 and IL-10 in cell culture supernatants were measured using enzyme-linked immunosorbent assay. The median level of IL-10 in PBMCs stimulated with PHA was significantly lower in acute asthma exacerbation compared with stable phase (464 vs. 859.5 pg/ml, p = 0.03). However, there was no difference in the level of IL-10 in PBMCs stimulated with Der p. The level of IFN- and IL-4 were not different between exacerbation and stable phase both in PHA and Der p-stimulated PBMCs. The decrease of IL-10 production in asthmatic children during acute exacerbation may emphasize the role of IL-10 in immune regulation in allergic disease.