Abstract: An electrical heating pad, in particular a mattress to be placed under a patient during surgery, comprising a number of partially overlapping resistor elements (11-18). The foil elements cover different regions of the pad and are positioned in an overlapping configuration such that in substantially all portions of the pad there are at least two overlapping foil element parts. Each foil element is fed separately from control circuitry so as to maintain a uniform temperature at all portions of the pad, irrespective of the heating load at different portions.