This paper reports the effects of Tripterygium Wilfordii (TW) on adrenal cortex in rats with adjuvant arthritis. Forty rats were divided into 5 groups. Adjuvant arthritis (AA) models were made with complete freund’s adjuvant (CFA) in groups I -IV. Each of which was treated with sodium carboxyl methyl cellulose, TW. prednisone and cyclophesphamide respectively. The untreated rats allocated to group V served as normal controls. The swelling of AA markedly subsided in groups I, I and IV as compared with group 1 (P<0. 01), whereas no significant differences were noted among groups I, I and IV (P>0.05). The obviously increased plasma corticosterone levels and decreased adrenal ascorbic acid levels were observed in group I, whereas decreased plasma corticcsterone levels and increased adrenal ascorbic acid levels were noted in group I. There was a striking contrast between groups I and I. The morphological changes of adrenal glands under light microscope revealed hypertrophic adrenal cortices in group I, and atrophie adrer.ai cortices in group I. The above findings suggest that the effect of promoting production of corticosteroids may be one of the mechanism by which TW can effectively treating autoimmune diseases.