Cowden's syndrome is a multisystem disease inherited as an autosomal dominant trait with incomplete penetrance and variable expression. The disease has typical oral manifestations which often precede more systemic involvement, and the dental professional is therefore well placed to institute a regime of regular checks to ensure early treatment of any neoplasms which may occur. However, since not all of the classical signs are present in all patients, diagnosis may be difficult. The case report of a patient with most of the features of Cowden's syndrome is presented and features compared with two other possible cases.