Abstract: Purpose : To study the morphological method to distinguish aneugens f rom clastogens. Methods : According to the morphological criteria micronuclei were classified and quantitatively analyzed induced by six reference mutagens (aneugens : colchicine , vincristin ; clastogens : cyclophosphamide , mitomycin C , ethyl methane sulfonate , gamma - ray) . Results : In comparing with the result s by clastogens , the f requency of circle micronuclei by aneugens was significantly increased( P = 0. 003) , ring micronuclei remarkably decreased ( P < 0. 0001) ,and crescent micronuclei did not change evidently ( P = 0. 07) . The 95 % confidence intervals of the mean micronucleus f requencies in class between the two types of mutagens were different very much , of which circle and ring frequences were completely separate. A discriminating function was acquired f rom the paper data. Conclusion : The f requencies of circle , ring and crescent micronuclei can be as a means to distinguish aneugens and clastogens.

Key words: micronucleus, aneugen, classification, discriminating analysis