Bladder pain syndrome (BPS) is a chronic, debilitating disease characterized by bladder and pelvic pain, irritative voiding symptoms (urgency, frequency, nocturia, dysuria), and sterile urine. Its etiology remains obscure and is thought to be multifactorial and related to a syndrome rather than a specific disease. There are many theories about its pathogenesis ,one of which is oxidative stress. Experts observed anomalies in each subcellular layer of IC/ PBS patients' bladder tissue,some of it could be a result of Reactive oxygen species (ROS). Reactive oxygen species (ROS) are an important byproduct of aerobic respiration and are mostly generated by mitochondria. Nitric oxide radical (NO) has effects on boosting vascular smooth muscle relaxation, which results in vasodilation and increases blood flow to the area of inflammation which we will estimate to find the possible relationship between (ROS) and IC.