Abstract: Animals:thirty male swiss mice were used in this experimetn.They Weredivided into 3 groups: GroupⅠ(5 males) was served as control; Group Ⅱ(15 males) was induced by thread with 20-Mc,Each thread "dose" containedaproximately 5 mg of 2o-Mc through the back skin of these animals;Group Ⅲ(10 males) was only used as a thread control. During a peried of 3 months,the results of the three experiment groups were as follows" In Group Ⅰ,therewas no change; Ib group Ⅱ, there were proliferative changes on the back skin.in addition, tumors induced by 20-Mc, is succesfully estabilshed,the rumors wereclassified as trichoepithelioma (5/15);keratoacanthoma(3/15), hasal cell epithe-lioma(1/15), and squamous carcinoma(1/15) ; In group Ⅱ,there were lightdegree changes in their skins.