The objectives of the study were to investigate the effects of wogonin on the cytotoxicity, natural killer activity, macrophage phagocytosis, release of interleukin-1alpha (IL-1alpha) and tumor necrosis factor-alpha (TNF-alpha), the expression of nuclear factor-kappaB (NF-kappaB) in leukocytes from Sprague-Dawley rats. Wogonin was added to the medium and the levels of IL-1alpha and TNF-alpha in the medium were measured using enzyme-linked immunosorbent assay. Both IL-1alpha and TNF-alpha mRNAs were measured by reverse transcription polymerase chain reaction and the levels of NF-kappaB and I-kappaB were measured by Western blotting. Natural killer cell activity and macrophage phagocytosis were measured by flow cytometry. The results demonstrated that wogonin induced cytotoxicity in rat leukocytes and promoted the activities of natural killer cells and macrophages. Wogonin increased the IL-1alpha and TNF-alpha levels in the leukocytes in culture media dose-dependently. IL-1alpha and TNF-alpha mRNA elevations were also promoted by wogonin. The data suggests that wogonin may affect the IL-1alpha and TNF-alpha mRNA expressions by affecting the NF-kappaB in rat leukocytes.