During four weeks in 1974, eight (26 percent) of 31 intensive care unit patients who had undergone open-heart surgery developed symptomatic Pseudomonas cepacia bacteremia in the intensive care unit one to three days after the open-heart surgery. An investigation demonstrated that operating room pressure transducers were being contaminated during cleaning with a detergent that contained P cepacia at the rate of 10(4) organisms per milliliter and that the organisms were transmitted to patients after open-heart surgery as a result of one to three days of contact with transducer-monitoring lines used in the operating room and brought to the intensive care unit with the patient. Pressure-transducer contamination, a frequently unappreciated but preventable cause of nosocomial bacteremia, can be minimized by sterilizing transducers between use on different patients by paying strict attention to aseptic technique when setting up, calibrating, and using monitoring systems; and by changing transducers, tubing, and monitoring fluid for each monitored patient at regular intervals.