The Doughty split tongue blade is used routinely with the Boyle Davis mouth gag during tonsillectomy. If the width of the slot in the blade is excessive, then the endotracheal tube may herniate through the slot in the blade and become fixed and inseparable from the blade. We report two cases of paediatric tonsillectomy where this potentially serious complication occurred. The slot widths of disposable and reusable Doughty blades were measured and specifications were obtained from several manufacturers. All disposable paediatric Doughty blades and some of the reusable blades were found to have excessively and potentially dangerously wide slots. Compression testing of endotracheal tubes by the manufacturer demonstrated marked increases in deformability on warming to body temperature. Ensuring that the slot width of the Doughty blade is not excessive for the endotracheal tube used is essential and we give recommendations.