The authors treated 13 individuais with Chagas disease, 4 in the acute phase and 9 in the indeterminate form of the chronic phase with a compound CL 71.366 of Lederle Laboratory. Different dosage schemes for the two groups were used. While the drug was relatively well tolerated by the majority of individuais all the chagasic patients after treatment continued with parasitaemia demonstrable by xenodiagnosis, although the control of cure was not the best. It is concluded that this drug is ineffective in the treatment of Chagas disease in the dosages utilised.