Carrier technology offers a promising approach for drug delivery system by coupling the drug to a carrier particle such as microspheres,nanoparticles, niosomes, liposomes etc. which modulates the release characteristics of the drug. Mucoadhesion had been a topic of interest in the design of novel drug delivery system to extend the residence time of the dosage form at the site of application or absorption and improve an intimate contact with the underlying absorption surface and enhance the bioavail ability or therapeutic performance of drugs. Mucoadhesive microspheres delivery system is an attractive concept, in which the drug can be entrapped inside the carrier to be released at the mucosal surface where the carriers are adhered due to their mucoadhesiveness. Nowadays mucoadhesive microspheres have been also developed for oral, buccal, ocular, nasal, vaginal and rectal routes for either systemic or local effects. The aim of this article is review the principles underlying the formulation and evaluation of mucoadhesive microspheres.