Radiation effects of poly (phenyl methacrylate) (PPMA) have been investigated by electron spin resonance (ESR) and Fourier Transform Infrared (FTIR) spectroscopy. The ESR spectrum observed for gamma irradiated PPMA at liquid nitrogen temperature (LNT) is a sextet (six line spectrum), while the spectrum appears to be broadened at room temperature (RT). Free radicals associated with the RT and LNT spectra are identified by the magnetic parameters employed to simulate the spectra. Thus, the ESR spectrum at LNT is found to be a superposition of components arising from the macroradicals of the type∼CH2–Ċ(CH3)–CH2∼(I) and a difference singlet spectrum due to phenoxy radicals C6H5Ȯ (II). The spectrum at RT is also simulated with the same values of magnetic parameters, employed to simulate the LNT spectrum, except for the value of the β-hyperfine splitting. Thus, the RT spectrum is thought to consist of two types of radicals I and II. The gradual decrease in intensity of the 1750 cm−1FTIR absorption band with the increase of radiation dose indicates the cleavage of the phenoxy carbonyl (-COOC6H5) groups of PPMA.