Chronic psychological stress cause erectile dysfunction (ED). Considering recent evidence that tumor necrosis factor-α (TNF-α) levels are increased in serum of patients with ED, the present study investigated the effects of infliximab (a TNF-α blocker) on endothelial nitric oxide synthase (eNOS) and neuronal NOS (nNOS) immunoreactivity of rat penile corpus cavernosum in unpredictable chronic mild stress (UCMS). Male adult rats were randomly divided into three groups (n=8 per group): Control, UCMS and UCMS+infliximab. Control and UCMS groups received physiological saline, UCMS+infliximab group received infliximab (5 mg kg