1) Eighteen cases with definite thymic lymph follicles were found among 1,356 autopsies. Eight of those were cases of Basedow's disease and the remaining 10 consisted of 2 cases of asthma syndrome one of which was associated with a type of allergic granulomatous angiitis, 1 case each of Wegener‐like granulomatosis, periarteritis nodosa, rheumatoid arthritis, aplstic anemia, chronic glomerulonephritis, acute yellow liver atrophy, Ekiri syndrome and purulent necrotizing tracheo‐bronchitis.2) No morphological differences were found between the thymic lymph follicles and lymph follicles in other organs. The folliculated thymus did not indicate any specific morphological features.3) Basically, in cases with thymic lymph follicles, the lymphatic tissue of other organs showed lymphatic follicular hypoplasia.4) Speculative explanation of the histogenesis and significance of thymic lymph follicle formation was attempted. ACTA PATH. JAP. 16:109‐130