Intracompartmental pressure in the leg was measured continuously during running in thirty-two patients who had either a medial or an anterior chronic compartment syndrome. It was found that on exertion the patients had significantly higher increases in pressure compared with the pressures in a control group. There were no remarkable differences between the two groups in terms of pressure at rest before exertion. After fasciotomy, the pressure returned to normal. The method that we employed to measure pressure can be use in diagnosing painful conditions of the leg.