Objective : To describe three acutely decompensated diabetic patients who suffered massive pulmonary embolism within 72 hours of admission. Design : Case series and literature review. Setting : University-affiliated urban hospital center. Patients : Three patients with severe hyperglycemia and ketoacidosis or hyperosmolar state who developed massive pulmonary embolism. Interventions : Intravenous heparin, recombinant tissue plasminogen activator, advanced cardiac life support. Results : Massive pulmonary embolism proved rapidly fatal in the two cases that manifested as pulseless electrical activity cardiac arrest. Conclusions : Critical care clinicians must recognize the potential for massive, lifethreatening pulmonary embolization in patients with decompensated diabetes.