Infiltrating lipoma is an unusual, benign, slowly growing neoplasm that characteristically infiltrates skeletal muscle and has a propensity for local recurrence if incompletely excised. These tumors rarely occur in the head and neck. A case of infiltrating lipoma of the retropharynx is reported. The clinical, histologic, surgical, and radiologic aspects of the lesion are reviewed. The use of magnetic resonance imaging of this tumor is presented.