Acute compartment syndrome is a serious complication of injury. It occurs when raised pressure within a closed osteofascial compartment compromises the circulation and function of tissues within the compartment. Most cases are caused by fracture. The largest group are tibial diaphyseal fractures, followed by soft tissue injury, crush syndrome, distal radial fractures and forearm diaphyseal fractures. Those at risk of developing acute compartment syndrome are young males, patients with bleeding disorders or on anticoagulant therapy and in the upper limb, high energy injury. The clinical symptoms and signs of acute compartment syndrome are pain, stretch pain and neurological abnormality, none of which are constantly present. Since early diagnosis of this condition is of paramount importance compartment monitoring is recommended. The recommended tissue pressure threshold for decompression has been variable through the years but should be related to the patient's blood pressure. A difference of less than 30 mmHg between the diastolic and tissue pressures has been validated clinically and it is recommended that at this level serious consideration should be given to decompression of the affected compartments. Use of this pressure threshold with compartment monitoring has been shown to half the delay to fasciotomy and significantly reduces the late complications of acute compartment syndrome.