The present paper reports the polymorphism occurring the three strains of Trypanosoma evansi found in South China (akinetoplast strain

horse strain and buffalo strain). A new form not previously reported is described here as a variant form. The cytoplasm and nucleus of this variant form is loose so that can be easily distinguied from the other forms such as slender form

short form and stumpy form. The average size of this new form is 20.2(l8.4～27.3)μm X 3.8(3.0～4.6)μm. It has been demonstrated by continous examinations of blood smears of infected mice for two full years that this variant form is a commonly present in all of the three strains of T. evansi in this country. This variant form can also be found in the blood smears of mice infected by the clones of the above three strains of T. evansi