Erythema nodosum (EN) is the most common cause of inflammatory nodules and usually affects the lower extremities and especially pretibial regions. EN may be idiopathic or associated with a wide spectrum of conditions including systemic diseases, infection, treatment with various drugs, pregnancy, and exceptionally with malignancies. The purpose of this study is to investigate the EN patients with different etiologies and laboratory features admitted to the rheumatology department and to compare them with other EN patients admitted to different departments including dermatology and infectious diseases. Totally, 107 patients diagnosed with EN (male/female: 37/70) were enrolled in the study. Of the 107 EN patients, 37 participants who were categorized as primary (idiopathic) EN (34.6 %) had not any underlying diseases or precipitating events. Majority of the participants were women (male/female: 12/25; mean age: 42.9 +/- A 9.2 years). Precisely, 70 EN (secondary EN) patients (65.4 %) had an underlying disease (male/female: 25/45; mean age: 36.1 +/- A 10.1). Beh double dagger et's disease (BD) was the foremost (n = 40, 37.4 %), followed by sarcoidosis (n = 17, 15.9 %), post-streptococcal (n = 9, 8.4 %), and other rheumatologic disease (one patient temporal arthritis, one patient Sjogren's syndrome, 1.9 %). Consequently, it is observed that BD, sarcoidosis, and post-streptococcal infection were found as the main etiologies of EN patients treated in our rheumatology department. These diseases should be kept in mind as an etiological factor in the management of EN.