['To avoid the use of unnecessary broad-spectrum antibiotics, empirical therapy of bacteraemia should be adjusted according to the results of blood cultures.', 'To investigate whether the results of blood cultures led to changes in antibiotic use and costs in a tertiary-care university hospital in Norway.', 'Medical records from all patients with positive blood cultures in 2001 were analysed retrospectively. Factors predisposing to infections, results of blood cultures, antibiotic use and outcome were recorded. The influence of blood culture results on antibiotic treatment and costs were analysed.', 'The antibiotic use in 226 episodes of bacteraemia in 214 patients was analysed. According to the guidelines empirical antibiotic treatment should be adjusted in 166 episodes. Antibiotic use was adjusted in 146 (88%) of these 166 episodes, which led to a narrowing of therapy in 118 (80%) episodes. Compared with empirical therapy there was a 22% reduction in the number of antibiotics. Adjustment of therapy was more often performed in Gram-negative bacteraemia and polymicrobial cultures than in Gram-positive bacteraemia. In bacteraemia caused by ampicillin-resistant Escherichia coli, ampicillin was mostly replaced by ciprofloxacin. The cost for 7 days adjusted therapy in 146 episodes was euro19,800 (23%) less than for 7 days of empirical therapy.'] Does adjustment of antibiotic treatment according to the results of blood cultures lead to decreased antibiotic use and costs?