Denileukin diftitox (DAB(389)IL-2 or Ontak) is a synthetic fusion protein with demonstrated efficacy in a number of lymphoproliferative disorders, including non-Hodgkin's lymphoma. We report the case of a 45-year-old man with progressive follicular large cell lymphoma following an autologous stem cell transplant treated with denileukin diftitox who developed a fatal skin rash associated with extensive erythema, edema and large bullae involving his entire body. The clinical features and pathology were compatible with toxic epidermal necrolysis. This is the first reported case of toxic epidermal necrolysis in the literature associated with denileukin diftitox.