Patients in intensive care units (ICU) are at high risk of developing pressure sores and the use of pressure sore risk tools has been advocated as a means of identifying patients at risk. A prospective multi-site observational study was conducted to define the incidence of pressure sores, assess two pressure sore risk scales and to define risk factors relevant to intensive care. Patients (n = 534) were assessed for the presence of pressure sores. The Waterlow and Jackson/Cubbin risk scales were completed each day for 314 and 188 of these patients respectively. A total of 75 pressure sores were recorded. Of these, 34 were present on admission. Of the remaining 41, 16 were classified as Grade 1 and 24 as Grade 2 sores. The pressure sore (PS) incidence was 5.2 per cent. Expressed as PS/1000 patient days there were 18.48 pressure sores per 1000 patient days. The ability of the risk scores to predict pressure sores was tested using a Receiver Operating Characteristic (ROC) analysis. The association of risk score with pressure sores was analysed using a survival function (Kaplan Meier) and variables compared using a logrank test (Mantel-Cox). Factors associated with pressure sore occurrence were developed and tested using a survival regression model. Both risk scales were poor predictors of pressure sores (ROC curve area approximately 70 per cent for both). The factors, coma/unresponsiveness/paralysed & sedated and cardiovascular instability were significantly associated with pressure sores with relative risks of 4.2 and 2.5 respectively. Risk increased as a function of time such that the cumulative risk was 50 per cent at 20 days.