Objectives: To determine which patient characteristics are associated with prolonged waiting times in the emergency department and which characteristics are associated with an increased risk of leaving without being seen. Methods: Multivariate analysis of routine data collected at the Northern General Hospital, Sheffield between 1 January and 31 December 2001. Patient age, sex, triage priority, postcode, initiator of attendance, mode of arrival, time, day, and month of presentation were examined as potential predictors of waiting time and risk of leaving without being seen. Results: Waiting time data for 71 331 patients were analysed, along with a further 5512 patients who left without being seen. Older patients and those with lower triage priority had longer waiting times, while ambulance borne patients had slightly shorter waiting times. Sex, source of referral, and postcode did not predict waiting times. The most powerful predictors of waiting time related to time of presentation, with longer waits being associated with presentation at night, on Mondays or Sundays, and during autumn months. Patients who left without being seen were more likely to be younger, male, lower triage priority, non-ambulance borne, self referred, and presenting at the times when waiting times were longest. Conclusion: Time of presentation, rather than individual patient characteristics, seem to be the most powerful predictors of waiting time. This suggests that concerns about inequity of waiting times should be addressed by reorganisation of staff duty rosters. P rolonged waiting times for patients in the emergency department are associated with reduced patient satisfaction 1 and an increased risk of leaving without being seen.2 This in turn is associated with high rates of representation and poorer health outcomes. 2 Waiting times have been increasing in the United Kingdom 3 and have been identified as a priority area by the UK Department of Health.4 5 As a result a number of initiatives have been introduced in an attempt to tackle this problem. 6 7 It is clearly important to reduce waiting times, yet it is highly unlikely that current initiatives will abolish waits completely. It is therefore also important that waiting times are equitable for individual patients. That is, differences in individual patients' waiting times should be, as far as possible, related only to clinical need. Waiting times act as a barrier to access to health care, and equity of access to health care is an important goal for the NHS. Data from Australia 9 suggest that waiting times are not equitable and that women, non-English speaking patients, self referred patients, or patients with a lower socioeconomic status are more likely to wait longer. To our knowledge, no study has yet attempted to discover if these findings are reproduced in the UK. The aim of this study was therefore to identify factors predicting prolonged waiting times for patients attending our emergency department and factors predicting which patients are most likely to leave without bein...