Use of solid-insulated high-voltage cable is being studied as a means of reducing the space requirements of transformer stations. A materials testing program appropriate to the mechanical loadings imposed on the insulation of the cable is described. In this the tensile, creep and fatigue properties of unfilled cross-linked polyethylene (XLPE), compounded ethylene propylene rubber (EPR), blends of XLPE with either EPR or cross-linkable butyl rubber (XLB) and carbon-filled semiconducting XLPE and EPR are investigated within the minus 30 degree C and plus 130 degree C temperature range. This article describes the test procedures and presents the results obtained.