Vascular access infections are a major cause of morbidity and mortality in hemodialysis patients, and the use of antimicrobials to treat such infections contributes to the emergence and spread of antimicrobial-resistant bacteria. To determine the incidence of and risk factors for vascular access infections, we studied hemodialysis patients at 7 outpatient dialysis centers (4 in Richmond, VA, and 3 in Baltimore, MD) during December 1997 to July 1998. Vascular access infections were defined as local signs (pus or redness) at the vascular access site or a positive blood culture with no known source other than the vascular access; and hospitalization or receipt of an intravenous (IV) antimicrobial. A total of 796 patients were followed for 4,134 patient-months. The vascular access infection rate was 3.5/100 patient-months, ie, patients had a 3.5% risk of infection each month. Independent risk factors were the specific dialysis unit where the patient was treated (relative hazard varying from 1.0 to 4.1 among the 7 centers), catheter access (relative hazard, 2.1 v implanted access), albumin level (relative hazard, 2.4 for lowest v highest quartile), urea reduction ratio (relative hazard, 2.2 for lowest v highest quartile), and hospitalizations during the previous 90 days (relative hazard, 4.9 for >/=6 v zero hospitalizations). These data confirm that vascular access infections are common in hemodialysis patients and that infection rates differ substantially among different centers. Catheter use should be minimized to reduce these infections. Additionally, the possibility that improved serum albumin and urea reduction ratio could reduce vascular access infections should be evaluated.