We have examined if lactic acid bacteria could suppress the toxic effect of bisphenol A. Lactobacillus casei YA-70 was chosen as representative. Thirty rats were divided into two groups (immature and mature) according to the weight. Each group was divided again into the control group (only alcohol treatment), bisphenol A treated group, and bisphenol A plus Lactobacillus casei YA-70 treated group. When 500 ppm of bisphenol A was fed everyday, 83% of immature group and 50% of mature group died within 3 weeks. Their internal organs, mainly livers and lungs, were changed in color and severely damaged. In the intestine of 5 ppm-fed group tumor-like nodules were observed. However, their number and size were markedly decreased when Lactobacillus casei YA-70 was supplemented in diet. This study strongly indicates that Lactobacillus casei YA-70 might play an important role to suppress the toxic effect of endocrine disruptor.