Background: Nummular eczema (NE) is predominantly a disease of adulthood that presents as coin-shaped plaques from coalescing papulovesicles. Clinical manifestations vary from minimal to severe. The pathogenesis of NE is still unknown. Objective: In this retrospective study, we sought to investigate the epidemiology, clinical manifestation, and abnormal laboratory findings in patients with NE. Methods: We identified patients with NE who had visited the department of dermatology in National Medical Center between 2012 and 2015. The clinical charts and laboratory tests from each patients’ medical record were reviewed. Results: Overall, 244 patients with a median age was 52 years were identified; two-thirds were men. The onset of lesions predominantly occurred in patients’ fifties and sixties. Predominant sites were the lower limbs, followed by the trunk and upper limbs. Twenty-six patients had a history of atopic diseases and 50 patients had elevated serum Ig E levels. The multiple allergosorbent test (MAST) was performed in 21 patients with an elevated serum Ig E level using an immunoblot assay. Dermatophagoides farinae, D. pteronyssinus, and house dust were common allergens found in MAST (76.2%, 76.2%, and 47.6%, respectively). Conclusion: In this study, we found that NE developed mainly in elderly patients and that lesions were distributed on the lower limbs. In addition, 44% of the patients had an elevated serum Ig E level and 76.2% of patients had a positive response to house dust mites on the MAST. We hope that these data will help to understand the characteristic of nummular eczema. (Korean J Dermatol 2018;56(2):114∼120)