BACKGROUND: French regulations require that adverse events involving medical devices be reported to the national healthcare safety agency. The authors evaluated reports made in 2005-2006 for patients in anesthesiology and critical care. METHODS: For each type of device, the authors recorded the severity and cause of the event and the manufacturer's response where relevant. The authors compared the results with those obtained previously from the reports (n = 1,004) sent in 1998 to the same database. RESULTS: The authors identified 4,188 events, of which 91% were minor, 7% severe, and 2% fatal. The cause was available for 1,935 events (46%). Faulty manufacturing was the main cause of minor events. Inappropriate use was the cause in a significantly larger proportion of severe events than minor events (P < 0.001) and was usually considered preventable via improved knowledge or device verification before use. Compared to with that in 1998, the annual number of reported events doubled and the rate of severe events decreased slightly (12-10%, P = 0.03). The rate of events related to manufacturing problems remained stable (59-60%, P = nonsignificant), and the rate of events caused by human errors was 32-42% (P = 0.01). There were no changes in the mortality rate (2% in both studies). CONCLUSIONS: The number of adverse events related to medical devices indicates a need for greater attention to these complex pieces of equipment that can suffer from faulty design and manufacturing and from inappropriate use. Improvements in clinician knowledge of medical devices, and to a lesser extent improvement in manufacturing practices, should improve safety.