Background: Despite the advent of safety measures to protect the health care workforce from contracting blood-borne diseases, nurses still sustain percutaneous injuries. We investigated the association between shift-level staffing and needlestick injuries. Methods: Shift-level staffing, patient occupancy, and acuity data were collected between 2003 and 2006 for the Military Nursing Outcomes Database (MilNOD), a multisite project that examined nurse staffing and adverse patient and nurse events. Data on needlestick injuries were obtained from occupational health/risk management reports and merged with MilNOD specific shift data. Hierarchical logistic regression, with Bayesian modeling, was used to analyze shift-level staffing, patient acuity, and workload as associated with needlestick injuries among nursing staff. Results: Of 108,000 shifts, 80 (<0.1%) had at least one needlestick injury occurrence, with 62 (78%) involving a contaminated needle. There was no difference in rate by unit type. Factors associated with needlestick occurrences on shifts were lower RN skill mix, a lower percentage of experienced staff, and fewer nursing care hours per patient per shift. Conclusion: Needlestick injuries continue to occur. An organizational culture of safety should emphasize the need for adequate staffing on every shift and extra vigilance during periods of high workload. Copyright © 2011 by the Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.