Bone morphogenetic proteins (BMPs) were first studied as growth factors or morphogens of the transforming growth factor-beta super family. These growth molecules, originally associated with bone and cartilage development, are now known to play important roles in morphogenesis and homeostasis in many other tissues. Recently, significant contributions of BMPs, their receptors, and interacting molecules have been linked to carcinogenesis and tumor progression. BMPs can sometimes play a role as a tumor suppressor. This article explains the composition and biological characteristics of BMPs, and investigates their new roles in the pathogenesis of cancer.