Animal model of chronic renal failure (CRF) was induced in wistar rats by 5/6 nephrectomy. Half of the rats were treated with Cordyceps sinensis (CS) in form of decoction. It was found that CS has mitogenic effect on spleen lymphocytes, and is capable of increasing the production of IL-2 from splenocytes of the CRF rats. IL-2 absorbency of the splenocytes was promoted by CS. CS also exhibited such therapeutic effects on CRF animal as to decrease the level of BUN and serum creatinine and to increase the level of hemoglobin. These results indicate that CS has a regulative effect on cellular immunity in CRF rats.