Water decoction of the leaves of Andrographis paniculata killed in vitro the microfilaria of Dipetalonema reconditum in 40 min. Three subcutaneous injections of the extract into infected dogs at 0.06 ml per kg body-weight reduced the number of microfilariae in blood by more than 85%. The larvae were not totally eliminated with more infections but the reduced microfilarial level persisted. No toxic effect of the extract was observed in rabbits. The treated dogs became lethargic initially for a week, probably due to the mass killing of microfilariae.