Starch, a cheap raw material which can be prepared in high quality grades is a widely used material in the pharmaceutical industry. Starch microspheres have been studied for years because of their biodegradable, bioadhesive and penetration enhancement properties. The starch microspheres have been suggested for embolization, parenteral administration and nasal or vaginal routes. Their bioadhesive properties, which induce a longer retention time in nasal and vaginal administration, make a system that permits the controlled release of the drug. Furthermore it is shown that by the use of starch microspheres intraarterially with the aim of embolization, diffusion of the drug to the tissues and cells at the ischemic site is enhanced while side effects are decreased. Starch microspheres are also used in the treatment of tumors with hyperthermia and in protection of healthy tissue from the hazards of radiation. In this paper, the structure of starch, types of starch microspheres, methods of preparation, characterization of microspheres, in vivo applications and their importance are reviewed.