The dependence of shear strength of epoxidized natural rubber (ENR)-based adhesives on molecular weight of the rubber is studied using coumarone-indene resin, gum rosin, and petro resin as tackifiers. The adhesive was coated on polyethylene terephthalate (PET) film substrate using a SHEEN hand coater at various coating thickness. The shear strength of adhesives was determined by a Texture Analyzer. Results show a maximum at 6.63 x 10(4) and 4.14 x 10(4) for ENR 25 and ENR 50, respectively, after which the shear strength decreases with further increases in molecular weight for all the coating thickness. This observation is attributed to varying degree of cohesiveness which culminates at the respective optimum molecular weight of ENR. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 3976-3979, 2009