This article examines the application of a simple technique for the collection of sweat to the investigation of tissue metabolites in 11 debilitated subjects attending a rehabilitation unit. It is applicable to subjects with a range of clinical conditions. Sweat was collected at the sacrum with the subjects either seated in a wheelchair or lying in bed, which was representative of their usual daily routine. The tissues could be loaded during sweat collection by sacral support in either of these positions. Collections were made for about 10 hours and interface pressures were recorded on at least two occasions. After the prescribed period, the sweat pads were removed and a quantitative analysis of a range of metabolites was performed. Metabolite concentrations may reflect local tissue viability and responses to loading. In unloaded tissues the metabolite concentrations were similar to those observed in nondisabled subjects in an earlier study. During prolonged loading at relatively low levels of pressure, there was elevation in the levels of some metabolites; for example 39 and 28% increases for lactate and urea respectively. Successive measurements on an individual over a period of months showed variations, which were small compared to those observed in either groups of nondisabled or debilitated subjects. These observations suggest that the technique may be best applied in clinical practice to monitor sequential changes in individual subjects.