We report here on a fatal case of abdominal gas gangrene. Two days after gastrectomy, a 56-year-old man presented with intractable abdominal pain and fever of a sudden onset, which quickly progressed over several hours to septic shock. Despite of the unexplained gas collections in the abdominal muscle, fascia, and subcutaneous layers on computed tomography scan, its clinical significance was overlooked. Emergency laparotomy was initially scheduled because of concern that there may have been a perforated viscus. At the time of monitoring for the anesthesia, we noticed marbled skin discoloration and the subcutaneous emphysema had spread on his flank. Shortly after the initial suspicion of gas gangrene, cardiac arrest developed during the arterial line cannulation. Despite prompt resuscitation measures, including the administration of catecholamines and the application of extracoporeal membrane oxygenation, he eventually died. Anesthesiologists need to understand this fulminant disease because extensive debridement under general anesthesia is essential for the treatment of abdominal gas gangrene. (Korean J Anesthesiol 2009; 57: 127~31)