Over the last decade the interest in intranasal delivery as a non-invasive route for drug administration has been exponentially increased. Since the nasal mucosa offers numerous benefits as a target issue for drug delivery, a wide variety of therapeutic compounds may be administered intranasally for topic, systemic and central nervous system action. The present paper reviews the relevant aspects of nasal anatomy, physiology and histology, and refers to the biological, physicochemical and pharmaceutical factors that must be considered during the process of discovery and development of nasal drugs as well as in their incorporation in appropriate nasal pharmaceutical formulations.