Chyle fistula is an uncommon serious complication of neck surgery, occurring in 1-3% of radical neck dissections. An untreated chyle leak is a potentially dangerous condition that may rarely lead to hypovolemia, hyponatremia, hypochloremia, hypoproteinemia and lymphopenia. Anatomic variants of the terminal portion of the thoracic duct and suction drainage in the neck wound play a primary role in causing this kind of lesion. Poor is the literature concerning chyle fistula, due to its rarity, and mostly case reports; still debated – prevalently empiric – is the management of this disease. The Authors report a case of chyle fistula following a reintervention of cervical bilateral lymphectomy for medullary carcinoma of the thyroid in a 75 years old female. In the reported case the chyle fistula was successfully treated conservatively, in early post-operative period with a low-fat diet and total parenteral nutrition, definitely followed by sclerosant therapy. The injection of a sclerosant agent (4 g of sterile medical talc diluted in isotonic sodium chloride solution) into the supraclavicular wound bed, through the drainage tube (clamped for 2 hours), determined rapid decline in fistula output, hence obviating surgical intervention.