A phototransient technique, previously described by Das Gupta and Tindell (1972), has been used to investigate trapping centres in low-density polyethylene in the energy range 0.05-0.25 eV. Trapping centres were found with activation energies of 0.19 eV and 0.08 eV at temperatures of 20 degrees C and -130 degrees C respectively. A linear change in activation energy with applied electric field was observed and was initially analysed using a linear Stark-effect-type shift. However, a more useful approach was found by determining the mobilities of carriers associated with a hopping process. These mobilities were calculated according to a theoretical model proposed by Mott and Gurney (1940), using trap densities described by McCubbin (1962).