Background Nurses are often responsible for placement of large-bore gastric tubes. Tube misplacement into the lungs is a potential complication with serious sequelae. The reliability of common bedside methods for differentiating between pulmonary and gastric placement has not been acceptable. Objective To compare the accuracy of capnometry (colorimetric indicator of end-tidal carbon dioxide) and air insufflation/auscultation with the accuracy of radiography in detecting the location of gastric tubes. Methods A prospective convenience sample of insertions of Salem sump gastric tubes was studied. Tubes were inserted by nurses according to the unit’s standard procedure, and air insufflation/auscultation, capnometry, and radiography were used to detect the position of the tubes. Results obtained with each of the methods were compared. Results A total of 91 tube placements were studied in 69 patients. No radiographically documented instances of lung placement occurred. Capnometry incorrectly indicated 15 of 91 gastric placements (16%) as placements in the lung. Air insufflation/auscultation incorrectly indicated 5 of 91 gastric placements (5%) as placements in the lung. Conclusions Neither air insufflation nor capnometry is a fail-safe method for determining placement of gastric tubes. Radiography remains the preferred method.