The abilities of therapeutic interchange (TI) and standard educational tools (SET) to change prescribing habits were compared. We evaluated the replacement of ciprofloxacin with levofloxacin in a four-hospital health system during a 14-month study period. Two hospitals used TI and two SET. The demographics, sites of infection, and severity of illness were analyzed for 554 patients treated at SET hospitals and 1323 patients treated at TI hospitals during a total of 2040 hospitalizations over a 14-month period. In TI hospitals, 97% of patients received levofloxacin, whereas 43% received levofloxacin in SET hospitals (p < 0.001). Clinical outcomes were not significantly different for the two groups, although more patients in the SET hospitals received combination antimicrobial therapy. Differences in savings per patient were significant between TI hospitals ($60) and SET hospitals ($37) (p < 0.001). The total annualized savings for all four hospitals was $156,444. TI was more effective than SET in facilitating changes in prescribing patterns in a health care system and resulted in significant cost savings to hospitals and payers.