The present study was conducted to determine the role of serum leptin at early diagnosis and differentiation between patients with manifestations of systemic inflammatory response syndrome (SIRS) and those with sepsis in patients suffering from a broad range of diseases in the intensive care unit (ICU) and its correlation with other biomarkers, such as C-reactive protein (CRP), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). This evidence concerns the gene IL6 and systemic inflammatory response syndrome.