Toxic epidermal necrolysis (TEN) is a potentially fatal medication reaction with a 30?tality rate. TEN is distinguished by massive keratinocyte death. The main effector cells appear to be cytotoxic T lymphocytes, and there is experimental evidence for involvement of both the Fas-Fas ligand and perforin/granzyme pathways. The best treatment for these people is still unknown. The withdrawal of the offending medicine and rapid referral to a burn unit are universally accepted protocols. Beyond that, however, there is substantial disagreement. There is evidence both for and against the use of IVIG, systemic corticosteroids, and other treatments. The vast majority of adverse cutaneous reactions to medicines are harmless and temporary. A select few, however, are critical and perhaps fatal. Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) and drug hypersensitivity syndrome (DHS), also known as drug rash with eosinophilia and systemic symptoms (DRESS), are the most serious. This review will concentrate on SJS/TEN, with occasional references to DHS.