Fascioliasis is the parasitic infestation of the liver and biliary tract related to Fasciola hepatica. Bithionol is proposed as the treatment of choice for human fascioliasis without major side effects. However, the efficacy of bithionol has been evaluated in chronic but not in acute fascioliasis. In this study we report on the success of treatment with bithionol in 10 patients with fascioliasis, 8 having acute fascioliasis. The criteria for the diagnosis of fascioliasis were hypereosinophilia, positive immunoelectrophoresis and indirect hemagglutination. Bithionol was given orally to hospitalized patients at the daily dose of 25 mg/kg body wt for 10 days. Three patients with acute fascioliasis received a second course of bithionol 2 or 3 mo after the first because of the recurrence of diarrhea and fatigue in one patient and persistent hypereosinophilia in two patients. All patients were cured. The follow-up period after the first course of treatment was between 16 and 47 mo. No major side effects were observed. We conclude that bithionol is the drug of choice for both acute and chronic fascioliasis. Moreover, its oral administration may allow treatment of fascioliasis in outpatients who do not have serious symptoms.