Abstract Background Early diagnosis of sepsis is the key for improving the survival. Culture is the diagnostic tool but the microbiological origin of infection is demonstrated in about 2/3rd of cases. Biomarkers have an important place in this process because they can indicate the presence or absence of sepsis and they are also important in evaluating the response to therapy and recovery from sepsis. Aim of the Work to find a correlation between the lactate clearance and mortality in patients with severe sepsis. Patients and Methods The study was conducted on 60 adult critically ill patients of both sexes with severe sepsis, who were admitted to the unit of Critical Care Unit in Ain Shams University Hospital. All participants were subjected to the following: detailed history, full laboratory and radiological investigations to diagnose sepsis including lactate level on presentation (0 hour), after 6 hours and after 24 hours, then lactate clearance is calculated and patients were divided to lactate clearance group and non-clearance group. Results The study showed that clearance patients significantly had lower mortality rate, SOFA score, vasopressor therapy duration, ventilation need and hospital stay days than the non-clearance patients. Conclusion Lactate is a good marker for predicting mortality and evaluating the initial resuscitation and management of severe sepsis and septic shock.