The prevalence of thyroid metastases in colorectal cancer (CRC) patients is unknown. We retrieved the records of all patients with CRC and pathologically proved thyroid metastasis for the period 1993-2004. Among 5,862 consecutive patients with CRC, 6 (0.1%) were diagnosed with thyroid metastases, a median of 61 months after the diagnosis of primary tumour, and a median of 19 months after the last surgical resection or radiofrequency ablation of other metastases (which were present in all cases). Signs and symptoms, when present (n=3), consisted of cervical pain, cervical adenopathy, goitre, dysphagia, and/or dysphonia. In other cases, the diagnosis was made by positron emission tomography scanning. Thyroidectomy was performed in the 5 patients with isolated thyroid metastases, with cervical lymph node dissection being required in all cases. The only patient treated conservatively because of concomitant liver and lung metastases developed life-threatening dyspnoea, which required emergent tracheal stenting. Median overall survival was 77 months, 58 months, and 12 months after the diagnosis of primary CRC, initial metastases, and thyroid metastasis, respectively. It is concluded that thyroid metastases are rare and occur late in the course of CRC. Thyroidectomy (with cervical lymph node dissection) may result in prevention or improvement of life-threatening symptoms and prolonged survival.