In the course of our research on the oligoglycosidic constituents of Turkish Astragalus species, we have isolated a number of cycloartane-type triterpene glycosides. The current study examines the immunostimulatory effects of nineteen of these cycloartane-type compounds using a transcription-based bioassay for Nuclear Factor kappa B (NF-kappa B) activation in a human macrophage/monocyte cell line, THP-1. All compounds were inactive at 100 mu g/ml except astragaloside I which increased NF-kappa B directed luciferase expression to levels about 65% as compared with maximal stimulation by E, coli lipopolysaccharide (LPS) at 10 mu g/ml. None of the compounds were active at Low dosage levels (0.1 mu g/ml) in combination with 50 ng/ml LPS. Astragaloside I also Increased mRNA expression of the inflammatory cytokines interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) as measured using reverse transcriptase-polymerase chain reaction (RT)-PCR, Based on these results it is clear that certain structural features are required for immunostimulation of cycloartane-type triterpene glycosides.