OBJECTIVE Endostatin is an angiogenesis inhibitor derived from type XVIII collagen. The aim of this study was to determine the concentrations of circulating endostatin in patients with systemic sclerosis (SSc), and to assess the relationship between these concentrations, extension of tissular sclerosis, and presence of cutaneous scars or ulcers. METHODS The study involved 50 patients with SSc and 30 healthy subjects. Cutaneous extension of sclerosis was graded according to Barnett's classification system: 33 patients had grade I SSc and 17 patients had grades II or III SSc. The results of pulmonary function tests were abnormal in 31 of 50 patients, 8 of whom also had abnormalities on chest radiograms. Cutaneous scars or ulcers were found in 22 of 50 patients. Endostatin concentrations were determined using a competitive enzyme immunoassay method. RESULTS The mean circulating endostatin concentration was significantly higher in the SSc group than in the healthy subjects group (mean +/- SD 53.2 +/- 22.4 ng/ml versus 9.9 +/- 9.7 ng/ml; P < 10(-4)), in patients with grade II or grade III SSc than in patients with grade I SSc (63.2 +/- 20.2 ng/ml versus 45.1 +/- 15.6 ng/ml; P < 10(-2)), in patients with abnormal findings on chest radiograms than in patients with normal findings on chest radiograms (67.6 +/- 22.4 ng/ml versus 50.4 +/- 21.6 ng/ml; P < 0.05), and in patients with cutaneous scars or ulcers than in patients without these manifestations (60.9 +/- 25.9 ng/ml versus 47.2 +/- 13.3 ng/ml; P < 10(-2)). CONCLUSIONS Circulating endostatin concentrations are significantly increased in patients with SSc. Production of endostatin may result from tissular sclerosis and could contribute to the development of ischemic manifestations.