Acute back pain is a common presenting complaint in the emergency department that leads to a great deal of resource utilization. The differential diagnosis is long and most cases are caused by benign pathology that will resolve on its own. Imaging is over-used and rarely helps. This article presents an algorithmic approach using red flags in the history and physical examination that will help physicians better identify the small of patients with serious conditions that, if untreated, will result in significant neurological damage.