#### Summary points Thyroid nodules are common: 4-7% of the adults have a palpable nodule, and up to 50-70% will have nodules on high definition ultrasonography, which may cause considerable concern to patients. In this article, we present an evidence based guide to investigating and managing thyroid nodules and we discuss the myths about nodules. Where relevant, we also highlight the differences between the two most widely used guidelines on this topic: the recently issued second edition of the British Thyroid Association’s guidelines on thyroid cancer1 and the American Thyroid Association’s guidelines.2 These guidelines were formulated by two large committees of experts, who reviewed all the available evidence, which mainly consists of prospective and retrospective cohorts; where there was no evidence, expert consensus opinion was used. Traditional teaching states that 20-40% of thyroid nodules are malignant.3 However, this pertains to a highly selected group of patients, with solitary cold nodules on scintigraphy.4 The risk of malignancy for a thyroid nodule identified on ultrasonography is much lower: 4-7%.5 6 Little evidence is available on referral times. Relying on expert opinion, the British Thyroid Association’s guidelines say that most thyroid nodules are benign and therefore do not require urgent referral to secondary care.1 This advice …