The gastric bypass (GBP) Operation is progressively being widely used to treat severe obesity. One problem with this operation is that it leaves the bypassed segment of the gastrointestinal tract not readily available for either mechanical, radiological or endoscopic evaluation. We have addressed this problem by putting a gastrostomy tube in the bypassed stomach at the time of the GBP. A radio-opaque marker placed around the gastrostomy site enables easy radiological localization of and thus easy percutaneous access to the bypassed stomach. The surgical technique is presented.