Cellulose-acetate electrophoresis (CAE) was used to investigate isozyme polymorphisms of 34 Group 1 and Group 2 isolates of Fusarium graminearum. Of the 26 enzyme systems screened, alkaline phosphatase, NADP-dependent glutamate dehydrogenase, peptidase D and phosphoglucomutase were found to be suitable for distinguishing members of Group 1 from members of Group 2. A great deal of similarity in the isozyme patterns among the isolates of a same group, independently of geographic origin, indicated that isolates within a given group are descendant from a same ancestral population. Significant differences in the isozyme patterns between the isolates of Group 1 and Group 2 indicated, however, that the two groups were of different ancestry. Group 1 isolates have since been named F. pseudograminearum. Due to the short run time, minimal need of equipment, small sample volume and staining requirements, CAE generally provides a rapid and accurate method for isozyme analysis of Fusarium species.