A relatively high incidence of amebiasis (E. histolytica) presumably exists in Guatemala, Costa Rica, and the interior of Panama. In the Hospital Santo Tomas in Panama City, however, only 13.9 per cent of a selected group of patients (from the men's medical, women's medical, and obstetrical wards) were found to harbor E. histolytica. In recent California surveys where comparable laboratory methods were used (wet fixed iron hemotoxylin stained smears examined) there has been reported an incidence of 9.8 to 16 per cent. Eighty-eight of the 101 Panama cases of amebiasis found on 1834 examinations were treated with Carbarsone (carbamino-phenyl-arsonic acid containing 28.8 per cent arsenic) given orally in average dosage of 5.0 grams for ten days. This amebacide was effective without adjuvant in clearing all but one of 37 cases that could be followed during the month of therapy. No evidence of arsenic toxicity was noted when total doses to 300 mgm. per kilogram were given orally.