Aim. To define the optimal treatment of postoperative ventral hernias. Material and methods. It was performed microscopic examination of intraoperative specimens which were obtained from 40 patients with medium, large and giant hernia. The aim was to reveal ultrastructural changes and morphological features which are associated with abdominal wall weakness in case of postoperative ventral hernia. There were 28 (70%) cases of primary postoperative hernia and 12 (30%) cases of recurrent and multiple-recurrent hernia. In 4 patients polypropylene mesh implants were implanted prior to recurrence. Tissue specimens were obtained from the top of herniation, hernial ring and in 6 cm from the hernial ring. Results and discussion. Electron microscopy showed that postoperative ventral hernias are accompanied by ultrastructural destructive changes in cells of the skin, aponeurosis and muscles that indicates on morphofunctional failure of abdominal wall tissues. Swelling and degradation of collagen, fibroblasts vacuolization, capillary sludge of erythrocytes, development of vacuum zones with the fragments of altered collagen fibrils, red blood cells and mast cells are morphological signs of micronecrosis followed by abdominal wall weakness and postoperative ventral hernias. Conclusion. Postoperative ventral hernias are associated with morphological and functional failure of abdominal wall due to tissue destructive changes. Therefore, this obviously defective tissue can not be used per se and especially with tension. Mesh implants should be applied.