The present study is an evaluation of bithionol treatment in established fascioliasis. Eight patients were enrolled in the study. All were passing eggs of Fasciola spp. and seven had concomitant Schistosoma mansoni infection. The clinical and haematological findings conformed with the known picture of fascioliasis. Bitin tablets (200 mg) were administered in the dose of 30 mg kg-1 body wt every other day for five doses. Eggs were counted during and for 4 months after the end of therapy. Fasciola ova disappeared after the second or third dose giving a cure rate of 100%. Ova of S. mansoni did not show any change in number. As regards the liver function tests; bilirubin, SGOT and SGPT values were within the normal range and were not affected by treatment. A raised SAP level was observed before therapy which was significantly higher after bithionol. Creatinine phosphokinase and lactate dehydrogenase enzymes and kidney function tests showed almost normal values and were not altered by therapy. It was concluded that Bitin was a potent fasciolicidal drug in the dose used. No side effects were observed.