Stevens-Johnson Syndrome (SJS), Overlap Syndrome (OS) and Toxic Epidermal Necrosis (TEN) are rare medical emergencies associated with a high morbidity and mortality. The literature on the characteristics of these diseases in Portugal is scarce. A retrospective study was conducted based on the clinical notes of the 20 patients admitted to São José Burn Unit in the previous 15 years with the diagnosis of SJS, OS or TEN. Most patients had TEN (65%), followed by OS (25%) and SJS (10%). Average age was 57,1 ± 19,0 years. The mean duration of stay in the Burn Unit was 12,6 ± 7,8 days. Mortality was 50%, being significantly higher than the 16,4% overall mortality in the general Burn Unit population in the same period (p < 0,01). The mean surface area involved was 43,9 ± 28,6 %. Allopurinol was the causal agent most frequently implicated (35%) followed by UV light exposure (15%). Fourteen patients (70%) were treated with steroids in the first days, whereas six patients were treated conservatively (30%). Mortality was inferior in the patients treated with steroids (42,8 vs. 66,7%), even though this difference did not reach statistical significance. Infection rates were not significantly different between the two groups. SCORTEN score proved to be a good predictor of mortality. Further studies are needed to reduce mortality in these diseases.