The aim of this study was to measure skin blood flow in patients with pressure sore in a long-term care unit. For comparison, measurements were also carried out on in-patients at risk of developing pressure sores and on healthy individuals in the same age groups as the in-patients. Skin blood flow was measured in the morning, using a laser-Doppler flowmeter. Measurements were made over the lateral part of the hip and over the lateral part of the upper arm. Measurements were carried out first at ambient temperature. The flow was then followed as the local skin region was heated to 40 degrees C. The results indicate that in healthy individuals the heat stimulus increased skin blood flow over the lateral part of the hip more than in in-patients in the same age group. Individuals below the age of 60 have a greater response than those over the age of 60. This impairment in the ability of the older in-patients to increase skin blood flow in response to thermal stimulus may be a factor in the development of pressure sores.