Objectives The purpose of this review was to determine the rate of those that leave the emergency department (ED) without being seen and their reasons, to clarify if such behaviour poses a health risk, to analyse the impact initiatives have made on the leave without being seen (LWBS) rate, and to discuss the implications of using it as a national performance indicator within the NHS.

Methods A combination of data sources was reviewed: a ‘realistic’ literature review, analysis of hospital episode statistics data from England and a local NHS trust audit.

Major Findings LWBS rates vary across the world, from 15% to 0.36%. Also initiatives to reduce LWBS rates demonstrated mixed outcomes, with reductions in the rate by as much as 96%, while others were ineffective. The most common reason quoted for LWBS was long waiting times and there were few data to suggest LWBS posed a risk to patient health.

Conclusions LWBS is an issue experienced in many countries that has responded in a varying manner to many initiatives in attempts to reduce it; however, it is clearly associated with the waiting times experienced in ED and therefore working within a packet of performance measures it would assess the effect of waiting times from another perspective.