Fifty five patients, with an history of chronic low-back pain, with or without leg pain, took part to the study. The fibrinolytic activity of these patients was studied after a 10 min occlusion test, aimed to enhance the fibrinolytic system. The presence of arachnoiditis was assessed by direct surgical observation or by unequivocal myelography plus CT scanner. The fibrinolytic defect entity appears not to be rare in our chronic low-back pain population and to be common in patients with arachnoiditis, the prevalence of fibrinolytic defect being respectively of 45% (25/55 patients) and of 75% (18/24 patients). The importance of a venous occlusion test to increase sensitivity (rejection of false positive) in the detection of a fibrinolytic defect and the relation between this defect and arachnoiditis, are discussed.