OBJECTIVES: To investigate mortality in men admitted to hospital with acute urinary retention and to report on the effects of comorbidity on mortality. DESIGN: Analysis of the hospital episode statistics database linked to the mortality database of the Office for National Statistics. SETTING: NHS hospital trusts in England, 1998-2005. PARTICIPANTS: All men aged over 45 who were admitted to NHS hospitals in England with a first episode of acute urinary retention. MAIN OUTCOME MEASURES: Mortality in the first year after acute urinary retention and standardised mortality ratio against the general population. RESULTS: During the study period, 176 046 men aged over 45 were admitted to hospital with a first episode of acute urinary retention. In 100 067 men with spontaneous acute urinary retention, the one year mortality was 4.1% in men aged 45-54 and 32.8% in those aged 85 and over. In 75 979 men with precipitated acute urinary retention, mortality was 9.5% and 45.4%, respectively. In men with spontaneous acute urinary retention aged 75-84, the most prevalent age group, the one year mortality was 12.5% in men without comorbidity and 28.8% in men with comorbidity. The corresponding figures for men with precipitated acute urinary retention were 18.1% and 40.5%. Compared with the general population, the highest relative increase in mortality was in men aged 45-54 (standardised mortality ratio 10.0 for spontaneous and 23.6 for precipitated acute urinary retention) and the lowest for men 85 and over (1.7 and 2.4, respectively). CONCLUSIONS: Mortality in men admitted to hospital with acute urinary retention is high and increases strongly with age and comorbidity. Patients might benefit from multi-disciplinary care to identify and treat comorbid conditions.