The interface pressures were measured between the sacrum, mid-lumbar spine and various support surfaces. Thirty healthy male volunteers were recruited. The spinal board, padded spinal board and vacuum stretcher were the support surfaces evaluated. We found high and potentially ischaemic pressures between the sacrum and the spinal board interface (mean 147.3 mmHg). This was reduced in the padded board (115.5 mmHg) but dramatically reduced with the vacuum stretcher (36.7 mmHg). It was also noted that no support was given to the normal lumbar lordosis by the spinal board (padded and unpadded), but support was given by the vacuum stretcher. This raises the question of how stable is an unstable spinal injury on a flat supporting surface.