A total of 36 ducks were utilised in this study ranging in age from 2 weeks upto 40 weeks of age. For histochemical parameters, the thyroid glands were separated out of the thoracic cavity and the required representative tissue samples were preserved in deep freeze maintained at -80oC. For scanning electron microscopy the tissue samples were processed by SAIF, NEHU, Shillong. The colloid showed a strong PAS positive reaction in all the age groups. The activities of both acid and alkaline phosphatases were present in all the age groups.The scanning electron microscopy revealed the normal structure of the thyroid gland in all the age groups. Parenchyma of thyroid gland was composed of follicles which were separated from each other by interfollicular connective tissue made up of collagen and reticular fibers. The follicles were closely packed together and their shape varied from oval to polyhedral. Microvilli of the follicular cells were observed on the apical surface. The SEM also showed the thyroid artery penetrating the gland.