Sepsis is commonly seen on the intensive care unit and almost all patients that die following intensive therapy unit care have evidence of an infection. There have been recent definitions of sepsis and organ failure following a consensus meeting of interested physicians and scientists. The role of biochemical mediators in the signs and symptoms of sepsis are becoming increasingly complex and better understood. The contribution of such mediators to the morbidity and mortality of sepsis is currently under investigation and there is much interest in the ability of drugs directed towards modifying these responses to alter the outcome from sepsis. An understanding of the relative roles of such mediators, along with the mechanisms regulating the release and activity of such compounds, is essential to comprehend the recent developments in this important area of our practice.