The prevalence of noncentral and central lines and the prevalence of nosocomial primary bloodstream infections was investigated in 72 representative German hospitals (NIDEP Study). Data from a total of 14,966 patients were documented. On the prevalence day, it amounted to 23.9% for noncentral and 5.1% for central lines. The total prevalence of nosocomial primary bloodstream infections was 0.3%, 8.3% of all nosocomial infections recorded were primary bloodstream infections. The device utilization rate of vascular catheters was retrospectively observed for both the prevalence day and another 6 days. The device utilization rate was 27.3% for peripheral and 6.1% for central catheters with higher rates in west Germany. The associated incidence density of primary nosocomial bloodstream infections per 1000 catheter-days was 0.3 for noncentral and 0.8 for central lines. In 61.4%, the primary bloodstream infections were microbiologically confirmed. In 52.6% of cases, Gram-positive bacteria were isolated (Staphylococcus aureus: 15.8%, other coagulase negative Staphylococcus species: 34.2%) and in 47.4%, Gram-negative ones (mostly: Escherichia coli: 13.2% and Klebsiella species: 10.5%). Prevention to reduce nosocomial bloodstream infections is possible by antimicrobial establishing specially trained infusion therapy teams, using antimicrobial or antiseptic impregnated bloodstream catheters and a strict review of the indication for a vascular catheter together with a minimization of catheter days.