I studied the results of fasciotomy of the affected muscle compartment in eight patients with chronic anterior-compartment syndrome (involvement of the anterior tibial compartment) and in nine patients with medial tibial syndrome (involvement of the deep posterior compartment), all of whom had pain with exercise. In the patients with chronic anterior-compartment syndrome, the preoperative intramuscular pressure in the anterior tibial compartment, as measured by the wick-catheter method, was increased ten minutes after exercise to 52 +/- 36 millimeters of mercury. After fasciotomy this pressure was significantly lowered to 4 +/- 6 millimeters of mercury (p less than 0.01). In the patients with medial tibial syndrome, the preoperative intramuscular pressure in the deep posterior compartment was normal ten minutes after exercise (8 +/- 4 millimeters of mercury) and did not significantly change after the fasciotomy (5 +/- 6 millimeters of mercury). The clinical results after fasciotomy were good in both groups of patients. There was complete relief of pain in all of the patients with chronic anterior-compartment syndrome and in five of the nine patients with medial tibial syndrome. The other four patients considered their condition to be improved in spite of some remaining symptoms.