Patients with thyroid cancer who undergo thyroidectomy are at risk of harbouring occult disease, owing to undetected tumour invasion of the lymph nodes; however, the extent of lymph-node examination required to determine this risk is unknown. Now, findings from a National Cancer Database study of 78,724 patients reveal that 53% of patients who were considered not to have occult disease, on the basis of examination of only a single lymph node, were falsely identified as 'node-negative'. Further analyses indicate that in order to rule out occult nodal disease with a 90% level of certainty, clinicians should examine six, nine and 18 nodes in patients undergoing thyroidectomy with stages T1b, T2, or T3 disease, respectively. These data provide the best available evidence to date on the extent of lymph-node inspection required to rule out the possibilty of occult disease in patients with thyroid cancer, and will hopefully result in better prognostification of patients following thyroidectomy.