Acute compartment syndrome represents one of the few true orthopaedic emergencies. Timely management is essential to prevent permanent sequelae. This video describes a case of acute compartment syndrome of the arm. Relevant patient history, physical examination, and laboratory findings are discussed, and a presentation of the operative technique for arm fasciotomy through a lateral approach is highlighted. Diagnostic criteria for acute compartment syndrome and indications for fasciotomy are reviewed, with a discussion of published outcomes after fasciotomy.