Background: Isoprostanes are prostaglandin-like end products of arachidonic acid peroxidation that are produced by a free radical-catalyzed mechanism. Considering its free radical-dependent formation and potent contractor effect, it is postulated that isoprostane 8-iso PGF(2alpha) may play an important role in oxidative stress-related smooth muscle dysfunction. These substances may also influence bladder activity directly by effects on the smooth muscle. The present study was designed to measure traditional biochemical parameters (MDA, TAS, vitamin E) in plasma and 8-iso PGF(2alpha) concentrations in urine of patients with spinal cord injury and to evaluate the relation of urinary isoprostane concentrations to the bladder function. Methods: All spinal cord patients underwent urodynamic evaluations. The biochemical tests were performed in both hyperreflexic bladder group (n = 23) and areflexic bladder group (n = 10), and the findings were compared to those of the patients with normally functioning bladder (controls, n = 19). Results: Urine 8-iso PGF(2alpha) concentrations were significantly increased in hyperreflexic group (median value 0.89 pg/mg creatinine) compared to both control (0.52 pg/mg creatinine) and areflexic groups (p < 0.001). The lowest concentrations of urinary 8-iso PGF(2alpha) were observed in the areflexic group (0.22 pg/mg creatinine), and these were positively correlated to the plasma MDA concentrations in areflexic patients (p = 0.05; r = 0.684). Conclusion: Isoprostanes may be involved in the pathogenesis of neurogenic bladder dysfunction. It may be of value to determine the urinary concentrations of 8-iso PGF(2alpha) in order to distinguish areflexic bladders from the hyperreflectics. (C) 2003 Elsevier B.V. All rights reserved.