Back pain is common in older adults, and also a common clinical symptom with many potential etiologies of life-threatening disease. Back pain is common in older adults, and also a common clinical symptom of many life-threatening diseases. Immediate recognition and exclusion of critical disease that causes back pain is important to physicians in order to prevent deleterious effect or mortality. So, we focus on the differential diagnosis of life-threatening back pain including acute coronary syndrome, aortic dissection, abdominal aortic aneurysm, renal infarction, vertebral compression fracture, spinal cord injury, malignancy, spinal infection, spinal epidural abscess and acute pyelonephritis. Complete history taking and physical examination are the keys to discover the underlying life-threatening disease. Although image studies are the essential survey for patients with back pain, the routine use of image studies do not improve outcomes. When the diagnosis is established, early initial treatment such as medication administration, antibiotic treatment or surgical intervention can reduce the morbidity and mortality. So we review several current principles about the algorism of approaching to the life-threatening diseases presenting as back pain.