This book highlighted the use of chitosan nanostructures in drug delivery, which facilitate the ability of the drug to cross the biological barriers. Chitosan has the desired properties for safe use as a pharmaceutical excipient. This has prompted accelerated research activities worldwide on chitosan nanoparticles as drug delivery vehicles. These systems have great utility in controlled release and targeting studies of almost all class of bioactive molecules as discussed in this book. Recently, chitosan is also extensively explored in gene delivery. However, studies toward optimization of process parameters and scale up from the laboratory to pilot plant and then, to production level are yet to be undertaken. Majority of studies carried out so far are only in vitro conditions. More in vivo studies need to be carried out. Chemical modifications of chitosan are important to get the desired physicochemical properties such as solubility, hydrophilicity, etc. The published literature indicates that in the near future, chitosan-based particulate systems will have more commercial status in the market than in the past.