We have shown that there is a direct relationship between the state (glassy or flexible) of the epoxy resin and its tree growth and space charge behaviour. At this stage it is not possible to relate directly the tree growth behaviour to the space charge properties of the epoxy resin. The main problem is that the tree growth characteristics were obtained using a 50 Hz alternating applied voltage and with a nonuniform electric field configuration (pin plane electrodes) while the space charge measurements were taken under steady DC electric fields with an initially uniform electric field configuration (parallel-plane electrode configuration). Electrical tree growth is driven by the high local electric fields surrounding the tree structure. The mechanical properties of the polymer network may therefore influence the potential for space (polarisation) charge to form in the resin surrounding a tree structure and therefore influence the local electric fields responsible for its growth. Much will depend on the ability of the resin network to deform locally in the high 50 Hz alternating electric fields surrounding the growing tree structure.