Two patients, a 58-year-old male and a 41-year-old female, who had poorly differentiated adenocarcinoma with signet ring cells of the stomach, developed progressive multiple organ failure following their surgical treatment, even though they did not have any direct surgical complications. Their abdominal explorations revealed primary gastric tumors with deep infiltration and metastases to the regional lymph nodes. Their clinical courses were characterized by acute renal failure and respiratory distress associated with disseminated intravascular coagulation. Histopathological examination at autopsy revealed diffuse cortical necrosis of the kidneys and marked congestion, edema, and hemorrhage with or without alveolar fibrosis of the lungs. Fibrin thrombi in the lesions of the kidneys and lungs strongly suggested the existence of disseminated intravascular coagulation. It is likely that the widely spreading cancer cells themselves produced the subclinical background for disseminated intravascular coagulation, which appeared to play an important role in the development of the multiple organ failure.