The purpose of this study was to evaluate the severity-of-illness score called SCORTEN with respect to its predictive ability and by using data obtained in the RegiSCAR study, the most comprehensive European registry of patients with Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). For advanced comparisons, an auxiliary score (AS) was defined using data obtained in a previous study. Three hundred sixty-nine patients with SJS/TEN were included in RegiSCAR between 2003 and 2005. The data needed for calculation of SCORTEN were available for 45% of patients. The score revealed a moderate predictive ability with a slight underestimation of the total number of in-hospital deaths by 11%, an area under the receiver operating characteristic curve of 0.75, and a Brier score of 0.14. Problems could be seen by analyzing subgroups such as patients with TEN. The AS was better calibrated but discriminated worse (area under the receiver operating characteristic curve: 0.72; Brier score: 0.14). With the help of a refined score derived from SCORTEN and AS, potential for a possible improvement could be demonstrated. The authors were able to show that the predictive ability of SCORTEN is acceptable. Although improvement might be possible, SCORTEN remains the tool of choice, whereas AS might be an alternative in retrospective settings with missing laboratory data.