Although soluble Fas ligand (sFasL) is an important candidate in toxic epidermal necrolysis (TEN) and Stevens-Johnson syndrome (SJS), Stur and colleagues report that elevated sFasL has been detected in maculopapular rashes. In addition to sFasL, other factors, including predisposing genetic factors, should also be investigated to determine their precise pathogenesis in TEN and SJS.