An epidemiologic investigation at a community teaching hospital identified 17 cases of endemic primary nosocomial bacteremias associated with the use of pulmonary artery catheters (PACs). A matched-case control study was undertaken to identify risk factors associated with these bacteremias. Factors significantly associated with bacteremia were length of hospitalization; length of stay in the critical care unit; length of time the PAC introducer was left in place and used as an intravenous (IV) access device after PAC withdrawal; respiratory compromise; PAC site infection; prior infections at other sites; concomitant hyperalimentation; and number of IV piggyback administrations per day prior to onset of bacteremia. Pathogens isolated included coagulase-negative Staphylococcus species (55.6%), Staphylococcus aureus (22.2%), Candida albicans (14.8%), and enterococci (7.4%). These pathogens were generally resistant to antibiotics given before the development of bacteremia. Bacteremia was associated with significant mortality, a prolonged hospital stay, and increased hospital charges. This study identifies important risk factors to consider in formulating guidelines to prevent and control PAC-associated nosocomial infections.