We recently described an equation for predicting the 1-year survival of critically ill patients aged over 70 years. The aim of this study was to check the performance of this equation in a validation group of 555 patients. The required demographic details (age, diagnosis, acute physiology score) of all elderly patients admitted between 1/4/95 and 31/9/96 were recorded and patients were followed for 1 year. One hundred and six patients died on the intensive care unit (19% mortality) and a further 134 died within 1 year (43% total 1-year mortality). The performance of the predictive equation was modest; the goodness-of-fit p-value was 0.04 and the area under the receiver operating characteristic curve was 0.75. For both groups, the combined 1-year survival of all critically ill elderly patients was 55% but the outcome of patients aged over 85 years remains poor (37%).