A new glycerol and maleic anhydride derivative of rosin (RGM) was synthesized and investigated for its film forming and coating properties. RGM was further evaluated for in vitro-in vivo degradation. Initially RGM was characterized for physicochemical properties, molecular weight (M-w) and glass transition temperature (T-g). Films were cast on a mercury substrate by solvent evaporation technique and characterized for mechanical (tensile strength, percentage elongation and elastic modulus), water vapor transmission and moisture absorption properties. Release of model drug, diclofenac sodium, was sustained up to 8 h from the RGM coated pellets at high coating level. The extent of coating level influenced the release rate. In vitro degradation study of RGM films was carried out in buffer solutions (pH 4.4, 7.4 and 10.4) at 37 ° C. The films were subdermally implanted in rats to study in vivo degradation. The extent of degradation was determined by weight loss and scanning electron microscopy. In vivo degradation of RGM was faster than in vitro. The results obtained promise the utility of RGM in drug delivery applications. © 2005 Elsevier B.V. All rights reserved.