The article presents the current knowledge on the etiology, epidemiology, pathogenesis, clinical signs, diagnosis, and treatment of erythema migrans (EM). EM is the most common clinical presentation of early localized Lyme disease (LD), the manifestation of infection caused by Borrelia burgdorferi. Multiple EMs are characteristic of the early disseminated stage. The development of EM can be accompanied by systemic symptoms, but they are not specific. In most cases, the fact of mite inoculation remains unnoticed by patients. Serologic tests often give false-negative results and are not required for diagnosis. For this reason, EM is usually diagnosed based on clinical manifestations. However, despite the typical clinical presentation of EM, which is considered to be the pathognomonic sign of LD, differential diagnosis with other types of figurate erythema and dermatoses characterized by irregular-shaped erythematous foci is required. Causal treatment of EM includes antibiotics. Timely started causal treatment at the early stage of the infection can result in cure of this potentially systemic infection, so timely diagnosis of EM is of great importance. The objective of this review is to draw attention of specialists to the problem of LD not only in endemic areas, to point out the need for diagnostic procedures, as well as timely antimicrobial and pathogenetic therapy, which will prevent the development of late-stage LD characterized by systemic lesion and, in some cases, disability.