The object of this article is to review the current knowledge about the acute compartment syndrome. The syndrome is caused by increased pressure in a muscle compartment and may result from several different conditions: fractures, contusions, haemorrhage, poisoning etc. The pathological physiology is complicated but the main theory is that progressive venous hypertension is involved and that this causes cessation of the microcirculation of the muscle concerned. The clinical diagnosis is described and pressure recording apparatus is reviewed. Treatment of the acute compartment syndrome consists of fasciotomy. Common sites are indicated and operative techniques suggested. Fasciotomy should be performed with compartmental pressures of about 30 mmHg. The untreated compartment syndrome will result in muscular fibrosis and nerve injury and will thus cause incapacitating conditions which may be avoided entirely if fasciotomy is performed in time.