Severe submandibular and ventral abdominal oedema was observed in an Asian elephant (Elephas maximus) in which liver flukes (Fasciola jacksoni) were recovered from the bile ducts at post-mortem examination. Clinico-pathologic examination of blood samples and serum from this elephant and another 8 elephants showed that most had anemia and hypoproteinemia. Fecal samples from 6 of the elephants contained from 6 to 83 eggs per gram. Treatment of elephants with nitroxynil (10 mg/kg) by subcutaneous injection produced severe local reactions at the injection site. Feces collected 2 and 4 months after treatment were free of trematode eggs. Hematologic values measured 4 months after treatment showed that the hemoglobin concentration, packed cell volume, erythrocyte count and plasma protein concentration had increased to within the normal range.