This book is related to a study involving development and in vitro evaluation of sustained release pellets of ambroxol hydrochloride prepared by extrusion spheronization followed by fluid bed coating with the commercial aqueous polyvinyl acetate dispersion (Kollicoat SR 30 D); aqueous dispersion of ethyl acrylate and methyl methacrylate (Eudragit NE 30 D) and aqueous dispersion of acrylic and methacrylic acid esters (Eudragit RL 30 D and Eudragit RS 30 D). The release of ambroxol hydrochloride from coated pellets was investigated at different coating level. The release mechanism was explored and explained with zero order, first order, Higuchi equation and Korsmeyer’s equation. The Mean Dissolution Time (MDT) value was calculated for all the formulations to determine the release retarding ability of the polymers. The results generated in this study showed that the profile and kinetics of drug release were functions of polymer type, polymer load and physico-chemical nature of the drug. This book will be helpful for the students and researchers of pharmacy discipline specially those who are engaged or interested in research related to modified release pellets dosage forms.