The distribution of visceral petechiae in patients whose deaths were caused by upper airway obstruction and disorders other than sudden infant death syndrome (SIDS) has not been systematically studied. The clinical and necropsy records and microscopic slides of 50 such cases were retrospectively reviewed. In cases in which the cause of death could reasonably be ascribed to lethal upper airway occlusion, petechiae were found only in thoracic viscera. When death was apparently not preceded by terminal changes in intrathoracic pressure, petechiae were found in viscera above and below the diaphragm. These findings suggest that intrathoracic petechiae occur as a consequence of pressure changes within the chest and indirectly support the hypothesis that the terminal mechanism in SIDS is upper airway obstruction.