We have reviewed the spectrum of gaseous densities in the soft tissues secondary to a perforated viscus. All patients presented late and most were elderly. The most common surgical procedure was diversion of the fecal stream proximal to the perforation. In our series 4 of 7 patients died in the immediate postoperative period. Knowledge of the mechanism and differential diagnosis of this entity will prevent overlooking this possibility, as occurs too frequently, particularly with subcutaneous emphysema of the leg.