Hospital discharge remains a particularly vulnerable time for adverse drug events, despite the use of medication reconciliation and other strategies to prevent medication errors at discharge. Previously, pharmacist involvement has also been shown to be beneficial in reducing medication errors, and even led to decreased readmissions in at least one study. However, in this randomized, controlled trial, approximately 50% of adult patients who received a robust pharmacist-driven intervention still experienced a clinically important medication error within one month following discharge for an episode of acute coronary syndrome or acute decompensated heart failure. The four-component intervention included pharmacist-assisted medication reconciliation, inpatient pharmacist counseling, low-literacy adherence aids, and individualized telephone follow-up after discharge. A case of a preventable readmission due to a medication error is discussed in this AHRQ WebM&M commentary.