The records of 32 patients with trabecular carcinomas of the thyroid gland were critically reviewed from a previously published serie of 138 thyroid cancers referred to the Centre Claudius Regaud, between 1952 and 1973. On the basis of clinico-pathological considerations, it seems possible to divide trabecular carcinomas into two groups. Pure trabecular carcinomas (moderately differenciated follicular carcinomas--WOH) which have a poor prognosis (5 years actuarial survival: 13%) related to high rate of local recurrences, fast metastatic spread to the lung, bad response to suppressive hormonotherapy and lack of 131 iode uptake by malignant tissue. Mixed trabeculo-vesicular carcinomas which have in comparison a fairly good prognosis (5 years actuarial survival: 63%) in keeping with a lower tendency to local recurrences and a useful concentration of radioactive iodine by metastases (most of them located in the skeleton) although dependent on the pourcentage of vesicles in the tumor process. Among differentiated thyroid carcinomas, distinction between pure trabecular and mixed trabeculo-vesicular carcinomas with quantitative determination of vesicules seems of great interest in relation to the therapeutic approach.