Objectives: To characterize the SCORTEN index obtained from 102 allergy patients having Stevens Johnson and Lyell (SIS& TEN) syndrome, during the period from January 2012 to June 2013, at the Center of Allergology and clinical immunology, Bach Mai hospital, study describes the process of retrospective in association with randomized. The results show that the ratio of male patients (58.8 percent) is higher than that of female patients (41.2 percent), where the average age of the patients is (46.6 + or - 20.2) years old. The patients at an age of 20 to 39 years account for highest ratio (35,3 percent), and the second highest ratio (32.5 percent) corresponds to the patients at their age ranging from 40 to 49 years, while the patients above 60 years old .have a ratio of 25.5 percent, where the lowest ratio (6.9 percent) belongs to the patients under 19 years old. The average value of SCORTEN index calculated for SIS-TEN patients is (1.05 + or - 1.08) points, more specifically from 0-1 points (77.5 percent), 2 points (14.7 percent), 3,points (2, 9 percent), 4 points (2.9 percent) and above 5 poi(lts (2 percent). The average SCORTEN index of SIS-allergy patients (0.85 + or - 0.70 points) is lower than that of TEN-allergy patients (1.71 + or - 1.70 points). When the SCORTEN index increases, the CPR, urea, creatinine, GOT, GPT, glucose and full blood bilirubin also increase, albeit blood albumin, blood cholestetol and HCO3- decrease. The dysfunction level of liver. and kidney experienced by SIS-TEN allergy patients is shown most obviously when the value of SCORTEN index is around 3 points.