A 17-year-old girl was admitted to the hospital for surgery of an enlarging, painful mass of the left calcaneus. Preoperative imaging studies suggested either a simple (unicameral) or aneurysmal bone cyst. Intraoperative biopsy of the lesion revealed a simple bone cyst with extensive cholesterol clefts. Such cysts are not uncommon in the calcaneus. However, the pathology of this case is unusual and often overlooked. The typical presentation, treatment, and pathology of these lesions are reviewed.