[en] Proanthocyanidins (a grape seed extract) possess a broad spectrum of biological activities. The present study was performed to investigate the effect of gamma radiation exposure and toxic sodium nitrites induced oxidative stress on the intestine and urinary bladder histologically and also to evaluate the possible protective role of proanthocyanidins. Seventy adult male albino rats, each weighing 95-105 g were used and divided into 7 groups as follows: The first group represents the control group. The second experimental group were exposed to 7 Gy gamma-rays as a single dose and sacrificed on the 7th day. The third experimental group received by a stomach tube daily 50 mg/kg b.wt of sodium nitrite for 4 weeks. The fourth experimental group received proanthocyanidins, Grape seed extracts (antioxidant) (100 mg/kg) body wt.) daily for seven days before irradiation and the continued for 14 days post irradiation. The fifth group of animals received grape seed extract after being exposed to gamma radiation for two weeks, while the sixth experimental group received the same antioxidant for seven days before and after received sodium nitrite (50 mg/kg) daily for 4 weeks. Finally, the seventh experimental groups was treated with the same antioxidant in same dose and time after received sodium nitrite for 4 weeks. The animals were then sacrificed on the end of each experimental duration. The results revealed that both gamma-radiation and sodium nitrite induced different histological changes in the intestine and urinary bladder of irradiated and sodium nitrite received animals. The effect of gamma radiation exposure showed marked degeneration of intestinal villi, vaculation in the lining epithelium cells and karyolytic nuclei. In addition, using sodium nitrite lead to necrosis of intestinal glandular cells. The effect of gamma radiation on urinary bladder was presented by, hyperplasia and vaculation of mucosal epithelium, congestion of blood capillaries. Rats from nitrite group revealed activation of glandular epithelium. The animals were treated with proanthocyanidins, the tissues revealed histological structure almost similar to the control group. This histological observations were performed to evaluate the efficiency of proanthocyanidins (a grape seed extract), through its antioxidant properties which might attenuate radiation or nitrite toxicity.