Cancer metastasis is a major determinant of cancer patient mortality. Mounting evidence favors a strong positive role for $TGF-{eta}$ in human cancer progression. The complex pattern on cross-talk of $TGF-{eta}$ and the related other signaling pathways is an important area of investigation that will ultimately contribute to understanding of the bifunctional role of $TGF-{eta}$ in cancer progression. This review summarizes some of the current understanding of $TGF-{eta}$ signaling with a major focus in its contribution to the tumor cell invasion and metastasis. Five issues are addressed in this review: (1) $TGF-{eta}$ signaling, (2) $TGF-{eta}$ and EMT, (3) $TGF-{eta}$ and MMP, (4) $TGF-{eta}$ and Ras, and (5) Role of $TGF-{eta}$ in invasion and metastasis. Due to the bifunctional cellular effects of $TGF-{eta}$, as a tumor promoter and a tumor suppressor, more precisely defined $TGF-{eta}$ signaling pathways need to be elucidated. According to the current literature, $TGF-{eta}$ is clearly a major factor stimulating tumor progression through a complex spectrum of the interplay and cross-talk between various signaling molecules. Understanding the role of $TGF-{eta}$ in invasion and metastasis will provide valuable information on establishing strategies to manipulate $TGF-{eta}$ signaling which should be a high priority for the development of anti-metastatic therapeutics.