Multiple endocrine neoplasia III (MEN III), also known as MEN IIb or mucosal neuroma syndrome, can often be recognized at an early age by its typical facies, marfanoid habitus, and characteristic mucosal neuromas. These features are usually present before development of the more serious, life-threatening complications that consist of medullary thyroid carcinoma (MTC) and pheochromocytoma. MTC associated with MEN III is generally aggressive with early metastasis. Early diagnosis is therefore crucial so that patients can be appropriately monitored for thyroid cancer with prompt thyroidectomy when indicated. Occasionally, patients present with C-cell hyperplasia of the thyroid, the histologic precursor to MTC. We describe a 16-year-old boy with mucosal neuromas, the typical facies of MEN III, gastrointestinal ganglioneuromatosis, and C-cell hyperplasia of the thyroid gland. Prompt thyroidectomy was performed, averting the risk of malignant transformation. Early clinical recognition of MEN III is crucial, as timely intervention can prevent the high mortality associated with MTC and pheochromocytoma.