Significant efforts have been devoted to use the potentials of nanotechnology in drug delivery since it offers a suitable means of site-specific and/or time controlled delivery of small or large molecular weight drugs and other bioactive agents.Pharmaceutical nanotechnology focuses on formulating therapeutically active agents in biocompatible nano forms, These systems offer many advantages in drug delivery, mainly focusing on improved safety and efficacy of the drugs, e.g. providing targeted delivery of drugs, improving bioavailability, extending drug or gene effect in target tissue, and improving the stability of therapeutic agents against chemical or enzymatic degradation. Mucoadhesive nanoparticulate Drug Delivery System prolongs the residence time of dosage form at the site of application or absorption. They facilitate an intimate contact of the dosage form with the underlying absorption surface and thus improve the therapeutic performance of the drug. This book is an effort to provide information on such mucoadhesive drug delivery systems that are developed for oral, buccal, nasal, rectal and vaginal routes for both systemic and local effect.