Résumé : The role of cassava was investigated in particularly severe endemic goiter area (Ubangi). Dietary intake of cassava induces an increase of plasma thiocyanate concentration and an increase of urinary excretion of stable iodine. Generalized iodine deficiency induces very high thyroid uptakes; the other parameters of thyroid function are more or less affected according to the dietary intake of thiocyanate. When thiocyanate intake is high an adaptation is obtained only at the expense of a drop of plasma T4 level and very high increase of plasma TSH.