Studies from around the world have shown that hospital-acquired infections increase the costs of medical care due to prolongation of hospital stay, and increased morbidity and mortality. The aim of this study was to determine the extra costs associated with hospital-acquired bacteraemias in a Belgian hospital, in 2001 using administrative databases and, in particular, coded discharge data. The incidence was 6.6 per 10 000 patient days. Patients with a hospital-acquired bacteraemia experienced a significantly longer stay (average 21.1 days, P < 0.001), a significantly higher mortality (average 32.2%, P < 0.01), and cost significantly more (average Euro 12 853, P < 0.001) than similar patients without bacteraemia. At present, the Belgian healthcare system covers most extra costs; however, in the future, these outcomes of hospital-acquired bacteraemia will not be funded and prevention will be a major concern for hospital management. (C) 2004 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved.