Six autopsy cases of non-traumatic gas gangrene in the abdomen are reported. Five of the six were caused by clostridia, as identified by culture or histology. There were associated underlying diseases, such as alcoholism, liver cirrhosis, diabetes mellitus, and malignant disease. Three of the six patients had gas gangrene in the liver. Bacterial proliferation and gas accumulation were found in the sinusoids of the liver, and congestion and edema with extensive gas embolism were found in the lungs. Pulmonary gas embolism was considered to be the direct cause of death in these three patients. The other three patients had intestinal clostridial gas gangrene, with alcoholism as an underlying condition. None of the six patients was clinically diagnosed as having gas gangrene. We suggest that gas gangrene should be considered in any patient with abdominal infection. A review of 19 autopsy cases of gas gangrene in the abdomen reported in the Japanese literature is also presented.