AIMS: Cannulated surgical instruments may retain biologic debris after routine cleaning and sterilization. Residual debris after cleaning is assumed to be sterile; however, there is no experimental basis for this assumption. The purpose of this study was to determine the sterility of retained biodebris found within cannulated surgical instruments after autoclave sterilization. MATERIALS AND METHODS: Fifteen cannulated drill bits were used to drill pig scapulae to create a plug of bone that was exposed to a mixture of Bacillus cereus, Pseudomonas aeruginosa, and methicillin-resistant Staphylococcus aureus for 60, 120, or 180 minutes prior to sterilization. The drill bits were autoclave sterilized using standard settings. The "sterilized" bone cores were then incubated in solution and streak-plated on blood agar. RESULTS: All 3 positive controls were positive for the experimental bacteria. Two negative controls were positive for contaminant bacteria. A B. cereus strain was recovered from 1 of the experimental group drill bits in the 180-minute group. Pulsed-field gel electrophoresis confirmed that the recovered B. cereus strain was identical to the experimental inoculate. CONCLUSION: Retained biodebris in cannulated drills may not be sterile after standard autoclave sterilization. In addition, delay of surgical instrument reprocessing may increase the risk of resistant contamination.