This is the first in a series of BMJ summaries of recommendations to improve patients’ safety, based on reports of safety concerns, incident analysis, and other evidence. The articles will highlight the risks of incidents that have the potential for serious harm and are not well known, and for which clear preventive actions are available. This summary is based on the safety report (rapid response report or RRR) from the NPSA in December 2008 on how to prevent overdose of midazolam. The RRR highlights evidence of harm and recommends key actions for staff. An accompanying article describes the process undertaken by the NPSA for developing rapid response reports, who to date have issued 22 RRRs.