Pig skin was exposed to approximately 80 joules of heat and electrical energy [50 Hz alternating current (a.c.) and direct current (d.c.)], respectively, under controlled conditions in order to find methods to document electrical torture. Biopsies were obtained immediately after exposure, and the morphology of the electrical lesions was compared with that of heat lesions and unexposed skin by using normal and polarized light microscopy. In areas exposed to 50 Hz a.c. and in cathode areas after d.c., where calcified collagen fibers have been found 2 days after injury, the collagen fibers showed a regular, densely spaced, cross-striation. This type of cross-striation was not found in heat or anode lesions. It was possible to blindly group all biopsies correctly with regard to influence of heat, 50 a.c. and d.c.