Blood fibrinolytic activity was measured in 18 subjects with severe chronic back pain and 18 age and sex matched controls. The patients showed evidence of defective fibrinolysis--namely, significant prolongation of the euglobulin clot-lysis time, reduction in fibrin-plate lysis-area and plasminogen levels, and increase in levels of the fibrinolytic inhibitors, alpha 2 antiplasmin and alpha 2 macroglobulin. This defect could be associated with fibrin deposition and scar formation and be responsible for the development and/or perpetuation of chronic inflammation and scarring at sites of damage in the spine. Enhancement of fibrinolytic activity may offer a new approach to the management of these back problems, and a double-blind controlled trial is in progress.