Drug error is a significant hazard to patient health. Poor, incorrect, and inconsistent labeling of injectable medicines and fluids, and the devices used to deliver these, has been identified as a patient safety issue. We report 5 cases of medication error as a consequence of incorrect or inappropriate labeling and analyze their cause. Recommendations for safe and practical labeling practices in anesthesia based on a review of the literature are presented. Implementation of the recommended labeling practices can reduce the risk of medication error and contribute to the safe administration of drugs.