Background : Sepsis-3 definitions were published recently and validated only in high-income countries. The aim of this study was to assess the new criteria’s accuracy in stratifying mortality as compared to its predecessor (Sepsis-2) in a Brazilian public intensive care unit (ICU) and to investigate whether the addition of lactate values would improve stratification. ; Methods : Retrospective cohort study conducted between 2010 and 2015 in a public university’s 19-bed ICU. Data from patients admitted to the ICU with sepsis were retrieved from a prospectively collected database. ICU mortality was compared across categories of both Sepsis-2 definitions (sepsis, severe sepsis and septic shock) and Sepsis-3 definitions (infection, sepsis and septic shock). Area under the receiving operator characteristic curves were constructed, and the net reclassification index and integrated discrimination index for the addition of lactate as a categorical variable to each stratum of definition were evaluated. ; Results : The medical records of 957 patients were retrieved from a prospectively collected database. Mean age was 52 ± 19 years, median SAPS 3 was 65 [50,79], respiratory tract infection was the most common cause (42%, 402 patients), and 311 (32%) patients died in ICU. The ICU mortality rate was progressively higher across categories of sepsis as defined by the Sepsis-3 consensus: infection with no organ dysfunction—7/103 (7%); sepsis—106/419 (25%); and septic shock—198/435 (46%) (P