Stevens Johnson Syndrome (SJS), and TENS (Toxic Epidermal Necrolysis Syndrome) another form of SJS—are severe adverse reactions to medication. Adverse drug reactions (ADR’s) account for approximately 150,000 deaths per year in the U.S. alone, making drug reactions the fourth leading cause of death in the United States. SJS is one of the most debilitating ADR’s recognized. It was first discovered in 1922 by pediatricians A.M. Stevens and F.C. Johnson after diagnosing a child with severe ocular and oral involvement to a drug reaction. Almost any medication including over-the-counter drugs, such as Ibuprofen, can cause SJS. Most commonly implicated drugs are anti-convulsants, antibiotics (such as sulfa, penicillin and cephalosporin) and anti-inflammatory medications.SJS and TENS are life-threatening reactions. If left untreated, they can result in death. Complications can include permanent blindness, dry-eye syndrome, photophobia, lung damage, chronic obstructive pulmonary disease (COPD), asthma, permanent loss of nail beds, scarring of the esophagus and other mucous membranes, arthritis, and chronic fatigue syndrome. The aim of present article is to provide in depth knowledge about Stevens Johnson Syndrome which is no doubt, a rare genetic disorder. In this article the author has explained all the clinical aspects related to Stevens Johnson Syndrome