The primary aim of our study was to establish what proportion of patients in the Emergency Department (ED) fulfill the criteria for sepsis. All adult patients presenting to ED in two 1-week periods, 6 months apart, were included. Notes were reviewed retrospectively to identify which patients fulfilled the criteria for sepsis and severe sepsis. The proportion of patients with sepsis was 4.3% (95% confidence interval 3.3-5.2%) and the proportion with severe sepsis was 2.2% (95% confidence interval 1.5-2.8%). In conclusion our results suggest that sepsis is more common than previously reported and this represents a significant burden on ED.