The involvement of microRNAs in human cancer is now well established. A few miRNAs function as oncogenes and many others display tumor suppressor activities. Several studies in the past few years have highlighted and reinforced a role for miR-203 as a tumor suppressor microRNA. This collection of in vitro studies give an initial and stimulating look into the many different means by which miR-203 can inhibit the various pathways involved in cell transformation and metastasis. Of special relevance is the ability of miR-203 to prevent proliferation of progenitor cells as well the epithelial-to-mesenchymal transition frequently associated with cancer progression and metastasis. Further more, the breadth of cancer types examined in these studies implicates miR-203 as a potential tumor suppressor gene whose re-expression or re-introduction into malignant cells could, by nature of its inherent pleiotropic effects as a miRNA, represent an important therapeutic tool used to combat a multitude of human cancers.