OBJECTIVES:: Adverse drug event (ADE) detection is a national priority. This study compares results from 2 ADE detection systems, voluntary reporting and computerized surveillance, at a large academic medical center. We analyze the medications most likely to cause harm, evaluate each systems' strengths, and propose a synergistic strategy for medication safety. METHODS:: Adult, inpatient ADEs from a 7-month period were evaluated and scored using a standardized methodology. ADEs per 1,000 patient days were calculated. RESULTS:: Surveillance detected 710 ADEs (6.93/1000 patient days), whereas voluntary reporting identified 205 ADEs (1.96/1000 patient days). For each major drug category (anticoagulants, hypoglycemia, narcotics and benzodiazepines, and miscellaneous), surveillance and voluntary reporting detected significantly different event rates (P < 0.001). Most surveillance events were hypoglycemia-related (68.2%, 4.72/1000 patient days), whereas most voluntarily-reported events were in the miscellaneous category (49.8%, 0.98/1000 patient days). The 2 systems detected statistically different ADE rates when stratified by nursing station. Of all unique ADEs (875), only 40 (5.6%) were common between the systems. CONCLUSIONS:: This study analyzes the results of 2 ADE detection systems used in daily hospital operations as well as a health system scorecard. Our aggregate analysis underscores the synergistic nature of these approaches. Although surveillance provides quantitative data to estimate the actual rate of ADEs, voluntary reporting contributes qualitative evidence to prompt future surveillance rule development and identify areas of emerging risk. In isolation, each system paints a partial picture, but together, they amplify our understanding of patient safety. © 2008 by Lippincott Williams & Wilkins.