Temperature rise, scaled to the square of rms electric field, was calculated for a model lead and electrode surrounded by different materials (ASTM phantom, blood, fat, and muscle.) Temperature rise at the electrode was greatest for the highest conductivity material (blood) along the lead body and least for the material with the lowest conductivity (fat). Muscle at the electrode yields the greatest temperature rise. The inclusion of a section of a heterogeneous inclusion along the lead body, tended to have a minor effect on the electric field transfer function. Electric field transfer functions were calculated and measured.