Summary 　The deaths caused by cancer increase in Japan and become a problem in the aging society. On the other hand, many epidemiological investigations have shown that obesity is the risk factor of various kinds of cancers such as colorectal, breast, endometrium and prostate cancers. The plasma concentrations of adiponectin are reduced in obese individuals, suggesting that adiponectin has anti-carcinogenic properties. Adiponectin binds to two types of receptors, AdipoR1 and AdipoR2, which are widely expressed in various cancer cells, although their expression levels have not fully characterized. Those facts suggest that adiponectin may play a positive role in the development and progression of various types of malignancy.