The plants of the Euphorbiaceae family, especially those of the genus Euphorbia, are frequently used by Brazilian folk communities to treat a wide variety of infectious, tumoral and inflammatory illnesses. Among the species of this genus, Euphorbia tirucalli L. is widely used in some Brazilian regions, such as the Jequitinhonha River Valley. There is evidence that the latex produced by E. tirucalli has antiviral and antitumor activities, but little is known about the mechanisms involved in these effects. It is likely that the mechanism for such activities involves leukocyte activation and cytokine production. In this work, we aimed to evaluate the production of type 1 (TNF-alpha and IFN-gamma) and type 2 (IL-4 and IL-10) cytokines by circulating leukocyte subsets submitted to brief stimulation with the crude latex of E. tirucalli. Peripheral blood leukocytes of twenty healthy subjects were submitted to 4 h incubation with crude E. tirucalli latex diluted in dimethylsulfoxide. After the incubation period, the cells were stained with FITC-conjugated monoclonal antibodies specific to the cell surface receptors CD4, CD8 and CD14, and to PE-conjugated monoclonal antibodies specific to the cytokines TNF-alpha, IFN-gamma, IL-4 and IL-10. The acquisition and analysis of data were performed by flow cytometry. The results showed a significant increase (p<0.05) in the percentage of CD4(+) T lymphocytes positive for the type 1 cytokines TNF-alpha and IFN-gamma. Neutrophils and CD8(+) T lymphocytes showed a mixed profile of cytokine production, characterized by an increase in the percentage of cells expressing IFN-gamma, TNF-alpha, and IL-10. The data indicate a predominant type 1 cytokine response. The findings presented suggest that the effect popularly attributed to E. tirucalli usage may be attributed to its effect on the production of TNF-alpha and IFN-gamma. However, the relationship between the in vitro and in vivo effects of E. tirucalli needs to be investigated.