Pathophysiology and management of pyrexia is described in detail. Management is made practical by dividing it as per the time of appearance of pyrexia, viz: within 24 hours post-operatively, 24 to 48 hours post-operatively, after 48 hours postoperatively, and after one week. Correlation of patterns of fever with pathogenic organism is given in the chapter, which ends with description of malignant hyperthermia, a rare condition.