Gamma irradiation effects on poly (ethylene glycol) (PEG) have been investigated by electron spin resonance (ESR) and Fourier transform infrared (FTIR) techniques. The ESR spectrum observed for gamma irradiated PEG is an asymmetric doublet, whose intensity distribution deviated from the expected values. The spectrum is simulated with the superposition of component doublet and component singlet spectra. Magnetic parameters of the component spectra are evaluated. From the values of magnetic parameters, structure of the free radicals has been predicted. As such, the observed spectrum is considered to arise from the free radicals of the type ~CHO . ~ (I) and ~CH O2 . (II). FTIR spectra of unirradiated and irradiated PEG have been recorded under different conditions. These studies indicate the formation of carbonyl terminated groups. ESR spectra have also been recorded for the PEG irradiated to higher doses of irradiation.