The effect of various radiations to a polymer is more complex and intense, compared to that in other materials, in view of the more complex structure and low bonding energies (5 10 eV for covalent bonds of the main carbon chain). Since the energy delivered to the polymer in most irradiations (including even beta and gamma rays of 1 to 10 MeV) exceeds this energy by many orders of magnitude, there is a high risk of radiation damage to all kind of polymers. However, engineering polymers (PC, PMMA, PVC, etc. and newer ones) as well as electro-active and other functional polymers (conducting polymers, polymer electrolytes) are finding ever increasing applications, often as nanocomposites, e.g. chemical and biomedical applications, sensors, actuators, artificial muscles, EMI shielding, antistatic and anticorrosion coatings, solar cells, light emitters, batteries and supercapacitors. Critical applications in spacecrafts, particle accelerators, nuclear plants etc. often involve unavoidable radiation environments. Hence, we need to review radiation damage in polymers and encourage use of newer tools like positron annihilation spectroscopy, micro-Raman spectroscopy and differential scanning calorimetry (DSC). Present review focuses on irradiation effects due to low energy ions (LEIs) and swift heavy ions (SHIs) on electro-active and engineering polymers, since gamma-and electron-beam-irradiations have been more widely studied and reviewed. Radiation damage mechanisms are also of great theoretical interest. Contents