One hundred seventeen patients had indwelling arterial illness for hemodynamic monitoring and blood sampling. The duration of catheterization varied from 25 to 439 hours, during which time no components of the system were replaced. In contrast to other reports, our study showed no instance of contamination of transducer dome fluid when the continuous flush device was located just distal to the transducer. The sampling stopcock showed bacterial growth in 16.2% of patients. In the one case in which the arterial catheter tip, stopcock, and patient's blood showed the same organism, culture of the transducer fluid was negative. Our results suggest that elimination of a static inline fluid column and proper aseptic sampling technique limit risk to the patient of transmitted bacterial infection from the fluid in the system. Routine changes of components of the system are not indicated and a substantial cost saving can be achieved.