There has been a growing awareness of the association between papillary thyroid carcinoma and familial adenomatous polyposis (FAP). The cases of four young patients with papillary thyroid carcinoma occurring with FAP are presented. Three patients underwent surgery to provide specimens for detailed histological examination. The surgical specimens showed well-encapsulated multicentric tumours exhibiting a predominantly papillary architectural growth pattern. In some areas, follicular architecture and cribriform patterns were noted. Atypical areas of spindle cells in a trabecular or solid configuration, which are not normally seen in classical papillary thyroid carcinoma, were evident. Malignant cells exhibited a graduation of cuboidal to tall cells with abundant amphophilic cytoplasm. The nuclei did not exhibit the typical nuclear clearing as seen in papillary thyroid carcinoma, but nuclear grooving and inclusions were noted. Psammoma bodies were not seen in any of the specimens. In a limited review of these patients, features such as young age at presentation, multicentricity and unusual histology suggest that thyroid carcinoma associated with FAP may represent a distinct form of thyroid cancer.