It is our main purpose in the present article to discuss treatment of the bleeding tendency so often seen in patients suffering from disease of the biliary tract. Bleeding from mucous surfaces often occurs spontaneously in these patients, but the greatest danger is from bleeding at operation or from the wound after operation. Through the work of several laboratories 1 it has been shown that a newly discovered vitamin, vitamin K, plays an important part in prothrombin formation in che body. Patients with obstructive jaundice or with biliary fistulas, having no bile in the intestine, have difficulty in absorbing such fat-soluble materials. Without adequate absorption of vitamin K they suffer from faulty formation of prothrombin, and for this reason a tendency to bleed develops. The therapeutic use of vitamin K in the treatment of jaundiced bleeders was first reported by Warner, Brinkhous and Smith 2 and almost simultaneously by Butt, Snell and Osterberg. 3 Additional cases were reported almost at once by Dam and Glavind. 4 All these reports have indicated that dramatic relief from the bleeding tendency is obtained in most cases by the administration of vitamin K. Further details of the literature on this vitamin may be obtained from the articles just cited.