A new value paradigm is taking shape in the drug delivery market. Nanotechnology delivery techniques will shape the future of drug delivery. "Nanotechnology-enabled drug delivery systems (DDS) over the next ve years are forecast to dramatically reshape the way existing drugs are delivered." The growing range of nanotechnology enabled drug delivery methods is poised to change the way new compounds are formulated, and to extend the life cycle of existing compounds. Nanoparticles hold promise as therapeutic agents for a number of diseases. In this book give a brief introduction regarding pulmonary drug delivery system. Determining the physicochemical characteristics of inhaled nanoparticles on their ability to cross the lungs alveolar epithelial surface is an important step in understanding the biological effects associated with exposure to these particles.