Background: Several publications reported different causes of erythroderma. Objective: The aim of this study was to determine the frequency of erythroderma and its aetiologies in Tunisian dermatology departments. Methods: This is a multicentric and retrospective study including all erythroderma patients in all Tunisian dermatology departments who consulted during a period of 5 years. Clinical and laboratory data were analysed. Results: Erythroderma was diagnosed in 127 patients; an incidence of 0.065% of patients is seen in dermatology consultations. In children (33 cases), the most frequent causes of erythroderma were ichthyosis (42.5%), seborrhoeic dermatitis (27.5%) and psoriasis (21%). In adults (94 cases), the main causes of erythroderma were psoriasis (41.5%), eczema (13%) and drug reactions (13%). Drug-related erythrodermas were specifically associated with fever and oedema (p = 0.0005) and eosinophilia (p = 0.01). Conclusion: No atopic erythroderma was observed, and eosinophilia was significantly associated with drug reactions.