Diagnosis of erysipelas is based upon the association of an acute inflammatory plaque with fever, lymphagiitis, adenopathy and hyperleukocytosis. These associated symptoms are variable (20-70 p. 100 of cases). Bacteriology is not helpful for the diagnosis of erysipelas because of a low sensitivity (hemoculture 5 p. 100, standard examinations 5-41 p. 100), or delayed positivity (serology). Moreover cutaneous bacteriology is difficult to assess when other bacteria than streptococci are isolated. Erysipelas have to be distinguished from non-necrotizing cellulitis by peculiar clinical features (such as erysipeloid, facial staphylococcal infection, Pasteurella, Haemophilus influenzae) and from necrotizing fasciitis. Some non-infectious diseases may mimic erysipelas such as venous thrombosis, familial Mediterranean fever, prosthesis intolerance, and compartment syndrome. Because the diagnostic value of clinical symptoms is not known and no diagnostic gold standard has been established, it is impossible to be sure that non-streptococcal erysipelas (especially staphylococcal) really exists. Thus, the first line treatment for all erysipelas must be an antistreptococcal antibiotic. Before prescribing a treatment, hemoculture and blood cell count could be useful. If antistreptococcal antibiotherapy is inefficient, all the differential diagnoses must be reviewed.