Dendrimers are new macromolecules synthesized in recent years, which are of great interests in many fields where they have potential important applications because of their hyperbranched, well defined and monodisperse structures. In this paper, the unique structures, general synthesis routes and basic physical and chemical properties of dendrimers are introduced in brief, and the progress in the research of dendrimers in drug (gene) delivery, contrast agents, cancer therapy were reviewed, as well as the perspective in research and applications.