AIM To determine whether admission delay (lead-time) and other factors are associated with hospital mortality rates of emergency medical patients. METHODS Patients presenting with emergency conditions during August to November 2009, and admitted to medical wards, including intensive care units, were enrolled. The time each patient spent in the ED, and other parameters were recorded. The primary outcome was the association between lead-time and hospital mortality. The secondary outcome was the association between lead-time and delta Modified Early Warning Score (MEWS) (MEWS at ward - MEWS at ED). RESULTS 381 cases were analysed. The overall mortality rate was 8.9%. By univariate analysis, the significant factors associated with mortality outcome were lead-time, ECOG (Eastern Cooperative Oncology Group) score, MEWS at ED, delta MEWS and sepsis. By multivariate analysis, the remaining significant factors were MEWS at ED, delta MEWS and sepsis. There was no significant relationship between delta MEWS and lead-time. In a sub-group of patients admitted to intensive care units, however, there was a positive correlation between lead-time and delta MEWS. CONCLUSION MEWS, delta MEWS and sepsis were predictors of hospital mortality in emergency medical patients. Lead-time was not associated with mortality, which could be due to benefits of various treatments initiated in the ED. In patients requiring intensive care, however, the longer lead-time probably led to higher MEWS and mortality.