[en] The dielectric loss behavior of crosslinked polyethylene has been determined over the frequency range 10-5 khz and over the temperature range -150 to 100⁰C. Major loss effects occur at the lower temperatures and are caused by liberation of the organic byproducts of the crosslinking agent, dicumyl peroxide. Analog materials prepared from linear low density polyethylene by blending in of either acetophenone or 2-phenyl-2-propanol confirm the hypothesis. The effects of concentration of byproducts and of orientation of the polymer have been studied. Activation energy analyses suggest that room temperature losses will occur in the microwave region. The behavior is significantly affected by curing with steam, typical loss peaks being an order of magnitude lower than for dry cured specimens. A new loss region appears close to but below, 0⁰C