Must meet at least one of the following criteria: Criterion 1: Patient has a recognized pathogen cultured from one or more blood cultures which is not related to an infection at another site. Criterion 2: Patient has at least one of the following signs or symptoms: fever (>100.4?F [>38?C]), chills, or hypotension, AND signs and symptoms and positive laboratory results are not related to an infection at another site, AND at least one of the following: 1. Common skin contaminant (e.g., diphtheroids, Bacillus sp., Propionibacterium sp., coagulase-negative Staphylococci, or micrococci) cultured from two or more blood cultures drawn on separate occasions. 2. Common skin contaminant (noted above) cultured from at least one blood culture from a patient with an intravascular line, and the physician institutes appropriate antimicrobial therapy. 3. Positive antigen (specific markers unique to that pathogen) test on blood (e.g., H. influenzae, S. pneumoniae, N. meningitidis, or Group B streptococcus).