Accumulating data suggest that activity of matrix metalloproteinases (MMPs) is increased in aortic dissection, and in thoracic and abdominal aneurysms. In the present study we sought to determine circulating stromelysin (MMP-3) concentration and its relationship with hypertension-induced aortic root dilatation. The study population included 42 patients with essential hypertension. The subjects were divided into two groups according to echocardiographically measured aortic diameter as those with aortic dilatation (n = 22) and without aortic root dilatation (n = 20). Plasma concentration of MMP-3 was determined by one-step sandwich enzyme immunoassay (EIA) method and compared in both groups. Baseline demographic properties were similar in both groups. Plasma stromelysin (MMP-3) level was significantly higher in patients with aortic dilatation than those without aortic dilatation (5.2 +/- 2.3 vs 3.3 +/- 1.9 ng/ml; P = 0.007). In conclusion, we found that circulating stromelysin (MMP-3) concentration was elevated in hypertension-induced aortic root dilatation.