In preliminary studies, on adult filarial parasites, difference in the electrophoretic pattern of glucosephosphate isomerase (GPI) of B. malayi, B. pahangi and the rat filarial worm, B. booliati, was demonstrated. There also appears to be a difference in the GPI and lactate dehydrogenase isoenzyme patterns of B. malayi (subperiodic) from different animal hosts. These observations suggest that the zymogram technique may yet prove to be a sensitive taxonomic tool for use in the characterisation of filarial helminths. At present, the contention is that the subperiodic form of B. malayi exists as a zoonoses (possibly also with B. pahangi), which is drawn from findings backed by procedures that cannot easily differentiate between closely-related species and subspecies. Thus enzyme electrophoresis could complement the parasitological methods currently used, and contribute in enhancing the validity of this contention. More work, and on a larger scale to include the microfilariae and infective larvae, would be required.