Upside down stomach (UDS) is a rare type of hiatal hernia. It is categorized by herniation of either the entire stomach or most of the gastric portion of the stomach into the posterior mediastinum. Acute UDS usually presents with abdominal and thoracic symptoms immediately after the stomach rotates, while chronic UDS often has either mild or no symptoms with the entire stomach rotated in the mediastinum. The first case was a 70-year-old female who was admitted with complaints of sudden vomiting and epigastric pain after eating. Computed tomography (CT) revealed UDS. Almost the entire stomach was twisted in the mediastinum, but the fornix was located in the abdominal cavity. After endoscopic reduction, the entire stomach was located in the mediastinum. Her symptoms disappeared and she was able to eat. The second case was another 70-year-old female with multiple hospitalizations due to frequent vomiting after eating. A review of previous CT scans showed a typical chronic UDS with the entire stomach located in the mediastinum. During her most current hospitalization, she was admitted with complaints of frequent vomiting and chest pain after overeating, and a CT showed UDS with only the fornix located in the abdominal cavity. Following hospitalization, the persistent vomiting disappeared and a CT scan at that point revealed that the fornix had returned to the mediastinum and she now had a normal UDS. These results indicate that chronic UDS caused acute symptoms due to "reverse incarceration" in the abdominal cavity through the diaphragmatic hiatus following eating. Chronic UDS is often either asymptomatic or only mildly symptomatic. However, these cases suggest that there is a mechanism whereby chronic UDS may cause acute UDS-like symptoms when the fornix becomes "reversely incarcerated" in the abdominal cavity following eating.