Adverse drug events (ADEs) remain one of the most common types of inpatient errors, affecting almost 5% of hospitalized patients, and lead to hundreds of thousands of emergency department visits and hospitalizations every year. Reporting ADEs is a crucial aspect of drug safety monitoring programs and international reporting standards are lacking. This study analyzed 108 ADE reporting systems and found significant variability in the data fields used to collect information. The authors suggest that standardization of data collection might improve drug safety monitoring by facilitating data aggregation on a larger scale.