Introduction: Leprosy patients may develop immune-mediated inflammatory reactions, which are the main cause of nerve function impairment and disability. Among them, Erythema Nodosum Leprosum (ENL) is a potentially life-threatening systemic condition. There are few data on ENL-associated morbidity and mortality, and the need of hospitalisation due to its complications. Material and methods: We conducted a retrospective cohort study including patients diagnosed at the Souza Araújo Outpatient Clinic, Rio de Janeiro. All patients had a first ENL episode at the clinic or were admitted to the Evandro Chagas Hospital, between 2005–2010. In 2014, we obtained the required data from the patients’ files to describe ENL morbidity and mortality, including treatment-related adverse events. Results: A total of 112 patients (72% male, median age at diagnosis 35 years, 83% had lepromatous leprosy) developed ENL, among the 676 patients diagnosed with leprosy during the study period. Most of the episodes were chronic and severe. Patients were treated with thalidomide and corticosteroids. Half of the patients receiving corticosteroids had adverse events. 14 patients were hospitalised, ten due to ENL complications. Six patients died, four during the ENL episode. None of these deaths could be considered directly caused by ENL or its treatment. Conclusion: In the group of patients studied, although a high morbidity due to the reaction itself and to the adverse effects of its prolonged treatment was observed, mortality due to ENL was not registered. Prospective studies are required in order to recognise leprosy complications, such as ENL, as consequential causes of death.