It is well established that small clinically undetected thyroid carcinomas can produce extensive lymphatic metastases. However, occult papillary carcinoma of the thyroid presenting as a large blood-borne metastasis and occult papillary carcinoma of the thyroid leading to death are both uncommon. The authors report two unusual cases of clinically occult carcinoma of the thyroid. The first case is a 2.4 mm microscopic carcinoma presenting as a large solitary pulmonary metastasis, and is one of the smallest reported primary papillary thyroid carcinomas presenting as a distant hematogenous metastasis. The second case represents a lethal carcinoma with extensive metastases not diagnosed until autopsy. These two cases effectively illustrate that the absence of a clinically detectable thyroid abnormality does not exclude the possibility of extensive hematogenous and lymphatic metastases from a minute or undetected carcinoma of the thyroid.