A 47-year-old woman had a swelling in the floor of the mouth and in the submandibular area on the left side. About four hours earlier, a dentist had extracted the mandibular left second premolar and first molar. The rate and degree of the distension were alarming; the floor of the mouth was at a level with the incisal edges of the mandibular incisors. Five hours later, the floor of the mouth was elevated about 1 1/2 cm above the incisal edges of the teeth. Treatment of the patient and her unusual sensitivity to meperidine and promethazine that caused a depression into Cheyne-Stokes respiration and hypotension are described.