A national, population-based laboratory surveillance of bloodstream infections (BSI) in Finland was performed. Blood-culturing rates were determined from data from clinical microbiology laboratories and trends in rates were evaluated using Poisson regression. During 1995-2002, 51,510 cases of BSI were notified; the annual incidence increased from 104 to 145 cases/100,000 (40%). Rates increased in all age groups but persons aged >or= 75 years accounted for 28% of cases and showed the largest rate increase. Escherichia coli, coagulase-negative staphylococci, Staphylococcus aureus and Streptococcus pneumoniae accounted for 58% of isolates and their relative proportions were unchanged over time. The annual blood-culturing rate increased by one-third during the study period but the number of BSI detected per blood cultures remained unchanged. Regional BSI incidence was significantly associated with blood-culturing rates. We conclude that the increase in BSI rates may have been due to more frequent blood culturing but was not associated with changes in the reporting system or aetiology of BSI.