Complaints are a vital component of clinical governance in healthcare systems. In a patient-focused NHS, it is important that healthcare professionals and organisations listen to, and act on, complaints from people who think they have been let down by the services they have received. This article reports on the results of a study of what prompts patients to complain after attending an emergency department (ED). As the results show, the complaint rate was 0.04 per cent. Among reasons why patients complained, non-clinical issues (63 per cent), such as poor communication and staff attitudes, and long waiting times, outnumber clinical issues (37 per cent). The study also highlights the need for greater direct supervision of junior staff, although this could be challenging given the current workforce pressures facing UK EDs.