Despite the widespread use of multiple dose vials (MDV) for anesthetic medications, there is a paucity of data concerning the sterility of in-use MDV. The purpose of this study was to analyze the frequency of bacterial contamination of MDV used in current anesthesia practice. The authors collected weekly samples from 351 in-use MDV for seven consecutive weeks and cultured them using appropriate bacterial growth media. The vials contained drugs including neuromuscular blockers, anticholinergics, and an induction agent. They were sampled from locations designated for elective as well as emergency surgery. Six vial subgroups were studied with multiple samplings for 6–48 days. One-half of all opened vials remained in use after 4–9 days, while less than 5% remained after 6 weeks. No vial yielded bacteria. The authors conclude that the incidence of MDV contamination with live bacteria is low for the anesthetic medications studied. This appeared to be true even for vials with increasing duration of use and for vials from locations where emergency surgery commonly was performed.