In the seriously ill, the paralysed and the elderly patient, many factors such as poor skin blood flow, malnutrition and immobility predispose to a high incidence of decubitus ulcers or pressure sores. The development of a sore is a complex process, but skin distortion and localized pressure are considered important precipitating factors. Over the last two decades manufacturers have produced a large variety of support surfaces claiming to be effective in prevention as well as treatment of sores. However, a review of available literature shows that none of the test methods used by different investigators has provided a comprehensive means of determining which device is appropriate for a particular patient. Many elderly, paralysed or seriously ill patients spend long periods of time in bed. They are prone to a high incidence of pressure sores due to factors such as malnutrition, immobility, elevated temperature and poor skin perfusion. The aetiology of a sore is complex and not yet fully understood, but it is widely accepted that the tissue damage is caused by prolonged localized pressure' 1 and skin distortion.2 2 The magnitude, duration and direction of pressure are considered to be the main causative factors leading to skin lesion. 3,4 Several names have been used to describe the damaged area, for example, decubitus ulcer, bed sore, trophic ulcer and distortion sore.