We studied patients who had flap necrosis after microsurgical reconstruction for orofacial defects. Among 64 patients, 5 had flap necrosis, resulting in a survival rate of 92.2%. All patients with flap necrosis underwent preoperative therapy. There was no significant difference in average age between patients with flap survival and those with flap necrosis; however, all patients with flap survival were younger than 50 years. The patients with flap necrosis had a significant decrease in postoperative pulse pressure, especially during the first and second postoperative days. Among the 5 patients with flap necrosis, 4 had a decrease in postoperative pulse pressure. Three patients concurrently had swelling in the submandibular and neck regions due to hematoma and underwent decompression procedures. On the basis of these results, we conclude that factors such as the postoperative pulse pressure and hematoma negatively affected flap blood flow.Early detection and elimination of these factors are considered essential.