1.A series of 298 cases of biliaryascariasis was diagnosed by contrastradiography of duodenum with ordinarybarium meal.All patients except those with grave complications were treatedconservatively with satisfactory results.2.Methods of x-ray examinationare described and discussed.3.The possibility of spontaneouswithdrawal of the worm from the biliarytract is proved and some of its mecha-nisms are suggested.4.Five illustrative cases are re-ported.It is shown that the presenceof the ascaris in the biliary tract maybe asymptomatic.