BACKGROUND The complications of warfarin therapy have classically been described as bleeding in the genitourinary and gastrointestinal tracts, skin, central nervous system, nose, penis, or retroperitoneum. However, rarely warfarin may cause bleeding that compromises a patient's airway. A sublingual haematoma is an example of such a complication. Only 10 previous cases of sublingual haematomas have been reported. METHODS We describe the case of a 56 year-old woman receiving oral anticoagulation who presented with a sore throat and hoarseness. Examination of her oral cavity revealed a soft, red, submucosal swelling involving the floor of mouth and ventral lingual surface bilaterally. No signs of airway compromise were observed. The patient's PT-INR was 10. Given the potential for rapid airway obstruction, the patient was admitted to a unit with closely monitored beds. Her coagulation disturbance was corrected medically and her haematoma resolved. The patient was discharged to the care of her family physician. CONCLUSIONS This case makes several important points. First, the case describes a rare, but life-threatening complication of warfarin therapy. Second, the initial signs of a sublingual haematoma are reviewed. Given the vagueness of these signs, diagnosis requires a high index of suspicion on the part of the physician. Finally, the case describes successfully management of this disorder without the use of a surgical airway. For this patient, reversal of her anticoagulation and vigilant monitoring saved her from having a surgical airway placed.