An outbreak of nosocomial Staphylococcus epidermidis bacteremia in a neonatal intensive care unit in 1981 was epidemiologically linked to use of Broviac central venous catheters (p = 0.05) and prompted a review of nosocomial infection surveillance data for the previous 6 years, which indicated a striking shift from gram-negative to gram-positive bacteria, especially coagulase-negative staphylococci, as major bloodstream pathogens. In a case-control study with 68 patients with bacteremia between 1979 and September 1981 and 64 control patients, stratified by birth weight, three risk factors were identified: use of Broviac central venous catheters, surgical procedures, and intravenous hyperalimentation. The risk factors varied with the birth weight category. In the group of cases and controls with birth weights less than 1500 gm, only the use of Broviac catheters, which are usually left in the superior vena cava for several weeks, was associated with subsequent bacteremia (odds ratio = 7.1, p = 0.001). These observations, as well as the temporal association of the introduction of Broviac catheters with the subsequent shifts in causes to gram-positive organisms, suggest that the long-term indwelling vascular access devices contributed greatly to the changing pattern.