RESULTS: A total of 7071 encounters with severe sepsis and/or septic shock were identified with a mean age of 60±16 years (mean±SD) and an overall mortality of 7.0%. 5499 (78%) encounters had severe sepsis alone, and 1572 (22%) had septic shock. Of patients with severe sepsis without shock, 3746 (68%) did not receive an ICD9 diagnosis code of 995.92. Diagnosed patients had a higher mortality (4.9% vs 2.16%, p<.00001), ICU admission rate (43% vs 24%, p<.00001), and hospital LOS (10.6 vs 8.19 days, p<.00001) when compared to patients identified by only clinical criteria. There was no difference in 30-day readmission rates between these two groups. Of the 1572 septic shock encounters identified, 629 (40%) did not receive an ICD9 diagnosis code of 785.52. Mortality was similar between septic shock encounters with an ICD9 vs clinical criteria (20% vs 21%, p=.588). Septic shock patients with an ICD9 code had higher ICU admission rate (79% vs 63%, p<0.0001) and 30-day readmission rate (29.7% vs 25.10%, p=.046). There was no difference in age, number of comorbidities, or number of organ dysfunction sites in patients with severe sepsis or septic shock who were identified by either method.