Four life-threatening dermatoses-Stevens-Johnson syndrome, toxic epidermal necrolysis, Kaposi's varicelliform eruption and purpura fulminans-are unique in their abrupt onset and rapid progress to death, but prompt diagnosis and proper therapy can often cure the condition or prevent undesirable sequelae. Since two of the four conditions can follow the use of a variety of drugs and all may be secondary to an infectious agent, any physician may encounter them in practice and should be aware of their seriousness.