Background and purpose Intermittent claudication in diabetes mellitus is commonly associated with arterial disease but may occur without obvious signs of peripheral circulatory impairment. We investigated whether this could be due to chronic exertional compartment syndrome (CECS).Patients and methods We report on 17 patients (3 men), mean age 39 (18-72) years, with diabetes mellitus-12 of which were type 1-and leg pain during walking (which was relieved at rest), without clinical signs of peripheral arterial disease. The duration of diabetes was 22 (1-41) years and 12 patients had peripheral neuropathy, retinopathy, or nephropathy. The leg muscles were tender and firm on palpation. Radiography, scintigraphy, and intramuscular pressure measurements were done during exercises to reproduce their symptoms.Results 16 of the 17 patients were diagnosed as having CECS. The intramuscular pressures in leg compartments were statistically significantly higher in diabetics than in physically active non-diabetics with CECS (p < 0.05). 15 of the 16 diabetics with CECS were treated with fasciotomy. At surgery, the fascia was whitish, thickened, and had a rubber-like consistency. After 1 year, 9 patients rated themselves as excellent or good in 15 of the 18 treated compartments. The walking time until stop due to leg pain increased after surgery from less than 10 min to unlimited time in 8 of 9 patients who were followed up.Interpretation Intermittent claudication in diabetics may be caused by CECS of the leg. The intramuscular pressures were considerably elevated in diabetics. One pathomechanism may be fascial thickening. The results after fasciotomy are good, and the increased pain-free walking time is especially beneficial for diabetics.