The authors have conducted a series of pressure sore prevalence surveys within one health district over a 4-year period Additional surveys of the availability and deployment of pressure redistributing (PR) bed mattresses have also been made within the same district The prevalence of pressure sores increased from 6 8% (1986) to 14 2% (1989) while the available stocks of PR mattresses increased from 69 (1987) to 186 (1989) Our results appear to question the common assumption that successful pressure sore prevention can be achieved through expanding the stocks of PR mattresses Five possible reasons why the increase m mattress provision was matched with an increased prevalence of pressure sores are forwarded The use of measures of prevalence rather than incidence rates to monitor the effects of clinical initiatives is discussed