Ischaemic priapism is characterised by hypoxia, hypercapnia and acidosis with resultant corporal fibrosis. Studies reported decreased erectile recovery after treatment of priapism longer than 36h. However, a recent study revealed that half of patients with 3days of priapism achieved recovery after T-shunt, although mechanism remains unclear. We aimed to investigate the effect of priapism duration on oxidative stress and antioxidant enzymes. Twenty-four male rats were divided into four groups. Group 1 served as control. Groups 2, 3 and 4 represented 1, 2 and 4h, respectively, of priapism induced by vacuum device and rubber band placed at base of erect penis. After 30min of reperfusion, penectomy and blood withdrawal were performed to investigate levels of malondialdehyde (MDA), protein carbonyl (PC), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx). Corporal MDA progressively increased with priapism duration (P=0.01). Corporal SOD significantly differed between groups 1, 2 and 4. Also, there were significant differences in corporal GPx in groups 1 and 4 (P=0.004) and groups 2 and 4 (P=0.01). Corporal CAT was higher in group 4, but multivariable analysis revealed insignificant differences. Plasma MDA of the experimental groups was significantly higher than that of controls. There were no differences among groups in terms of other parameters. Increased antioxidant enzymes according to duration of priapism suggest that immediate treatment to relieve oxidative stress should be initiated in prolonged cases. However, further studies should be conducted to determine resistance mechanisms of the corpora to prolonged ischaemia.