This article focuses on defining the principles of bioadhesive delivery systems based on hydrogels to biological surfaces that are covered by mucus. An overview of the last decade’s discoveries on mucoadhesion and applications of mucoadhesive hydrogels as drug carriers is given. Techniques that are frequently used to study the adhesion forces and physicochemical interactions between hydrogel, mucus, and the underlying mucosa are reviewed. Mucoadhesion can be defined as a state in which two components, of which one is of biological origin are held together for extended periods of time by the help of interfacial forces mucoadhesion is the attachement of the drug along with a suitable carrier to the mucous membrane. Mucoadhesion is a complex phenomenon which involves wetting, adsorption and interpenetration of polymer chains. Thereafter, several researchers have focused on the investigations of the interfacial phenomena of mucoadhesion with the mucus. The polymers used for formulation of mucoadhesive drug delivery systems are poly acrylic acid derivatives, chitosan and newer second generation polymers. Mucoadhesive drug delivery systems with its various advantages have a lot of potential in formulating dosage forms for various chronic diseases.