The relevant phenomena influencing the space charge accumulation in epoxy insulators for gas insulated systems are studied by space charge measurements in plate-shaped epoxy samples according to the pulsed electroacoustic (PEA) method. In space charge measurements according to the PEA-method the signals are disturbed by attenuation and dispersion. The factors alpha and beta representing attenuation and dispersion respectively, are determined for the materials under investigation. The space charge distributions are reconstructed from the originally measured signals by eliminating the influence of attenuation and dispersion by calculation. Two different Al2O3-filled epoxies are studied. In both materials homo charges accumulate close to the ground electrode, indicating charge carrier injection. At higher temperatures hetero charges accumulate in one of the materials under investigation. No hetero charge accumulation occurs in the second material.