Staphylococcus aureus is an important cause of exit site infections and peritonitis in patients receiving continuous ambulatory peritoneal dialysis. To determine the role of Staphylococcus aureus nasal carriage in determining the rate of Staphylococcus aureus exit site infection and peritonitis, we studied 177 continuous ambulatory peritoneal dialysis patients who were followed up at Queen Mary Hospital from January 1990 through June 1995. The cumulative rate of exit site infection was one episode per 11.5 patient months. The cumulative rate of peritonitis was one per 19.2 patient months. The total number of patients with one or more positive cultures of Staphylococcus aureus from the anterior nares was 30 (16.9%). There is a significant association of the Staphylococcus aureus nasal carriage status with Staphylococcus aureus exit site infection and peritonitis. Moreover, there seems to be a trend for the Staphylococcus aureus nasal carrier to run a higher risk of multiple episodes of Staphylococcus aureus-related infections. Thus for this group of patients, decolonisation of Staphylococcus aureus from the anterior nares with local or systemic antibiotics may be useful.