Abstract: Objective:To analyze the etiology,clinical features and treatment of the erythema nodosum（EN）.Methods: A total of 117 patients with a diagnosis of EN between 1993 and 2007 in our hospital were included in the study retrospectively.Results: It affected mainly middle-aged people,and the propotion of men and women was 1∶1.5.The foremost aetiology was streptococcal infection（30.77%） followed in decreasing order by tuberculosis infection（25.64%）,unknown causes（21.37%）,rheumatic and immunologic diseases（16.24%）,suspect tuberculosis infection（5.13%）,lymphoma（0.85%）.The outcomes were usually favourable.Conclusion: EN is a multiple-factor diease,closely involved with infection,and the common infections are caused by streptococcal bacterium and tubercle bacillus.The other factors included rheumatic immunologic diseases and malignant tumors.Etiology and heteropathy treatment are very importent.