The treatment of lover limb erysipelas rests on antibiotic therapy directed against streptococci, but the necessity of prescribing a concomitant anticoagulant treatment has not yet been established. The incidence of deep vein thrombosis in patients with erysipelas of the leg in unknown. In a prospective study of 40 patients presenting with this type of skin disease, we looked for deep vein thrombosis, using systematically pulsed Doppler vein exploration combined with ultrasonography and, if necessary, a second Doppler examination and a phlebography. Six cases of deep vein thrombosis were diagnosed. This complication was observed in 5 patients at high risk for deep venous thrombosis; it had never been foreseen at clinical examination.