OBJECTIVE: Priapism is a persistent and often painful penile erection in the absence of sexual stimulation. It can cause progressive fibrosis, edema and drying of the erectile tissue and then it can lead to erectile dysfunction. Previous studies suggested that, neuronal nitric oxide levels increased during the priapism. High NO levels can result in the formation of reactive oxygen species (ROS) leading to oxidative stress in tissue and reproductive system. The aim of this study was to evaluate oxidative and nitrosative effects caused by priapism in cavernosal tissue and serum, and determinate beneficial effects of lycopene on ischemic priapism.