The effects of Astragali radix extract on interleukin (IL)-6 and tumor necrosis factor (TNF)-α productions, prostaglandin E₂ (PGE₂) biosynthesis, and leukotriene C₄ (LTC₄) production from lipopolysaccharide (LPS)-stimulated human amnion cells were investigated. Amnion cells produced detectable amounts of both IL-6 and TNF-α under LPS-stimulated conditions. Astragalus extract inhibited the production of IL-6. However, TNF-α production was not inhibited by the extract on L929 cytotoxicity assay. Treatment of amnion cells with LPS for up to 24 h resulted in an increase in PGE₂ release in a concentration- and time-dependent manner. The extract (150 mg/ml) significantly inhibited the output of PGE₂ by amnion cells (p<0.01). The arachidonate lipoxygenase metabolite (LTC₄) was increased by LPS treatment of amnion cells. Astragalus extract (30 mg/ml) inhibited LTC₄ production by approximately 65% throughout the culture period. These results suggest that Astragali radix extract may have a role in inhibiting bacterial infection-associated preterm labor by suppressing the productions of IL-6, PGE₂, and LTC₄ by human amnion cells.