This chapter contains sections titled: Introduction Polysachharide Sources of Chitin and Chitosan Composition of Chitin, Chitosan and Cellulose Chemical Modification of Chitin and Chitosan Chitin – Chemical Modification Chitosan – Chemical Modification Depolymerization of Chitin and Chitosan Applications of Chitin and Chitosan Bio-medical Applications of Chitosan Miscellaneous Applications Antimicrobial Properties Film-forming Ability of Chitosan Function of Plasticizers in Film Formation Membranes In Wastewater Treatment Multifaceted Derivatization Potential of Chitin and Chitosan Conclusion