Medication-related clinical decision support is a ubiquitous component of computerized provider order entry (CPOE). Alerts are intended to reduce medication errors and may improve adherence to recommended treatments, but they have yet to improve clinical outcomes. This cross-sectional study examined how often inpatient providers overrode clinical alerts as well as whether those overrides were appropriate. Over 3 years, clinicians overrode nearly 340,000 alerts. While nearly all duplicate drug alert and drug allergy overrides were appropriate, most renal or age contraindication overrides were inappropriate. Although this single institution investigation of a homegrown, older CPOE system may not be generalizable to more common electronic health records, it does illustrate how alert fatigue compromises patient safety. A previous WebM&M commentary discussed the challenges of designing safe CPOE.