In order to modify the properties of poly(ethylene terephthalate) (PET), P(ET/CL) copolymers were synthesized by addition of polycaprolactone(PCL) in the polycondensation of PET oligomers. The feed compositions of PCL was varied up to 60%(wt) of total reactants to obtain copolymers containing up to 58% CL units. Properties of copolymers were determined by IH and 13C-NhtR, DSC, GPC, TGA and intrinsic viscosity experiments. IH and 13C-NMR analysis of copolymers revealed new peaks assigned to the alkyl group adjacent to the ester groups whose environment is different from those in PET or PCL. NMR analysis of the extract evolved during the transesterification reaction showed the presence of a caprolactone derivative along with ethylene glycol. Detailed analysis of the NMR results suggest that copolymerization of P(ET/CL) has indeed occurred through transesterification. At the higher feed compositions of PCL, the intrinsic viscosity of the resulting copolymers tended to be higher. Copolymers from 40 and 60%(wt) PCL feed composition were of higher molecular weight than PCL. Copolymers exhibited a single Is which decreased with increasing PCL lied composition suggesting that the respective monomers are distributed in a random manner, rather than in blocks. This also suggests that under the conditions of copolymerization employed transesterification between PET oligomers and polycaprolactone occurs extensively. Copolymers of PCL feed composition 30, 40, 60%(wt) do not exhibit crystallization or melting and appear to have a potential as elastomeric material.