Abstract: Apparatus for inducing thrombosis in a blood vessel subjacent a surface 14 of a living human or animal body comprises a therapeutic electrode 15, 21, 22, 23, 24, in the form of an inflatable balloon which is flexible enough to conform to the surface, and which maintains the electrode in contact with the surface and restricts the flow of blood through the blood vessel during induction of thrombosis therein. Direct current is flowed through the electrode as anode and a counter cathode to coagulate the blood in the blood vessel adjacent the anode. The apparatus is useful to treat active oesophageal variceal bleeding, in which application the electrode 15 may have the general form of a Sengstaken-Blakemore oesophageal tamponade tube.