Niridazole, a nitrothiazole derivative, was tried in 32 patients with amebiasis. It is effective in both amebic dysentery and hepatic amebiasis, and gave a cure rate of 77.7 and 72.7%, respectively. Electrocardiographic changes were observed in 53.1% of the patients. In eight patients who could be followed, the EKG changes reverted to normal in 2 to 4 weeks after the end of therapy. Confusional psychosis was observed in two patients, one of whom died during treatment. The exact cause of death could not be ascertained even after autopsy.