The rising incidence of immunocompromised-patient infections caused by bacteria that are normally nonvirulent and indigenous to normal flora has focused attention on the contamination rate of blood cultures. This contamination is usually a consequence of the mode of collection or processing within the laboratory. The contamination rates of blood cultures usually are reported to a hospital's quality assurance component and to the medical staff. In addition, the identification of organisms isolated from blood cultures is reported to the physician, regardless of whether the organism isolated is a contaminant or the infectious agent. Consequently, reporting positive blood cultures that reflect contamination in certain cases may trigger some physicians to initiate prompt antibacterial therapy. The contamination rate of the blood culture has, therefore, a serious impact on medical consequences as well as on resource use.