Background: For most of the population a serious acute illness that require an emergency admission to hospital is a rare "once in a life time" event. This paper reports the one year mortality of patients admitted to hospital as acute emergencies compared to the general population. Method: This is a post-hoc retrospective multicentre cohort study of acutely admitted patients from October 2008 to December 2013 aged 40 or higher. It compares the observed one-year mortality of both acute medical and surgical patients with the overall mortality in the general population at comparable age bands. Results: We included 18,375 patients and 4037 (22.0%) died within one year. For all age groups the one year mortality of those admitted to hospital for acute illness was markedly greater than for the general population. Although the odds ratio of death was highest in younger patients (e.g. odds ratio >. 20 for 40. year olds), the absolute risk of death was greatest in the elderly (e.g. 20% mortality rate for men admitted to hospital over 65. years of age, compared to 1.7% for the general population). Discussion: Admission to hospital for an acute illness is associated with a greatly increased risk of death within a year and for many elderly patients may be a seminal event.