A review of all medication incidents reported to the National Reporting and Learning System (NRLS) in England in Wales between 1 January 2005 and 31 December 2010 was undertaken. The 526 186 medication incident reports represented 9.68% of all patient safety incidents. Medication incidents from acute general hospitals (394 951) represented 75% of reports. There were relatively smaller numbers of medication incident reports (44 952) from primary care, representing 8.5% of the total. Of 86 821 (16%) medication incidents reporting actual patient harm, 822 (0.9%) resulted in death or severe harm. The incidents involving medicine administration (263 228; 50%) and prescribing (97 097; 18%) were the process steps with the largest number of reports. Omitted and delayed medicine (82 028; 16%) and wrong dose (80 170; 15%) represented the largest error categories. Thirteen medicines or therapeutic groups accounted for 377 (46%) of the incidents with outcomes of death or severe harm. The National Patient Safety Agency (NPSA) has issued guidance to help minimize incidents with many of these medicines. Many recent incidents could have been prevented if the NPSA guidance had been better implemented. It is recommended that healthcare organizations in all sectors establish an effective infrastructure to oversee and promote safe medication practice, including an annual medication safety report. In the future, preventable harms from medication incidents can be further minimized by; the continued use of the NRLS to identify and prioritize important actions to improve medication safety, a central organization continuing to issue medication safety guidance to the service and better methods to ensure that the National Health Service has implemented this guidance.