For investigating the effects of a combination therapy of triptolide (TP) with glycyrrhizin (GL) in rats with collagen-induced arthritis (CIA), the arthritic index was examined, and the levels of anti-CII IgG, TNF-alpha and IL-10 in serum were measured by ELISA. Our results showed that combined triptolide and glycyrrhizin treatment (TP 13.40 microg, GL 26.78 mg) can reduce the arthritic index of CIA rats and decrease the level of anti-CII IgG and TNF-alpha in serum. The observed effect was similar to the one measured upon application of TP 17.86 microg, GL 26.78 mg and TP 17.86 microg. The level of IL-10 was not significantly different among the rats of the TP 17.86 microg, of the TP 17.86 microg, GL 26.78 mg and of the TP 13.40 microg, GL 26.78 mg groups while the IL-10 levels in rats of the TP 13.40 microg and GL 26.78 mg groups were significantly higher. Combined triptolide 13.40 microg and glycyrrhizin 26.78 mg can therefore significantly inhibit collagen induced arthritis, and the effect was similar to the one of triptolide at 17.86 microg.