Pressure sores are a problem, especially in elderly patients. Our study was designed to determine the effectiveness in pressure-sore prevention of a new interface-pressure decreasing mattress. In a prospective randomised controlled clinical trial we tested the Comfortex DeCube mattress (Comfortex, Winona, USA) against our standard hospital mattress in 44 patients with femoral-neck fracture and concomitant high pressure-sore risk score. In addition both groups were treated according to the Dutch consensus protocol for the prevention of pressure sores. On admission and 1 and 2 weeks after admission, pressure sores were graded. The two groups were similar in patient characteristics and pressure-sore risk factors. At 1 week, 25% of the patients nursed on the DeCube mattress and 64% of the patients nursed on the standard mattress had clinically relevant pressure sores (grade 2 or more). At 2 weeks the figures were 24% and 68%, respectively. The maximum score over the several body regions of the pressure-sore grading, measured on a 5-point scale, was significantly different in favour of the DeCube mattress at 1 week (p=0·0043) and 2 weeks (p=0·0067) postoperatively. We show that the occurrence of pressure sores and their severity can be significantly reduced when patients at risk are nursed on an interface-pressure decreasing mattress.