The Sapporo Cancer Seminars have been held annually since 1981. The 28th Sapporo Cancer Seminar was held on 26-27 June 2008 at the Hokkaido University Conference Hall, focusing on transforming growth factor (TGF)-β signaling and cancer. More than 150 scientists participated in the seminar, and it provided a great deal of information on the role of TGF-β signaling in carcinogenesis and tumor metastasis. The possible use of TGF-β antagonists for treatment of cancers was also discussed at the seminar.