It has been said that thyroid gland controls the function of salivary gland and vice versa. In an attempt to investigate the role of submaxillary gland on the function of thyroid gland, the authors have observed the changes of thyroid gland histologically and histochemically at 70 days after removal of submaxillary gland in rats. The results are as follows: 1. There are no significant changes of thyroid cells after submaxillary gland removal. 2. The colloidal concentration of thyroid follicles is markedly decreased after submaxillary gland removal. 3. The colloids of thyroid follicles show intensive reaction to PAS staining in intact rats, but moderate or minimal reaction in submaxillary removal rats.