Ultrasonography has become an important imaging modality for the evaluation of small structures, suchas thyroid glands, lymph nodes and adrenal glands, because it is relatively inexpensive, it is non-invasive andit does not require general anesthesia. Both normal and abnormal small structures can be seen, though thisdepends to a great extent on the quality of the equipment and the operator skills. For thyroid glands, it canbe used to assess thyroid carcinomas, canine hypothyroidism and feline hyperthyroidism. Ultrasonography isalso a very valuable modality for evaluating superficial and abdominal lymph nodes. By combining differentultrasonographic criteria, it is possible to accurately differentiate normal from reactive or malignant lymphnodes. Finally, the adrenal glands can be evaluated ultrasonographically in cases of hyperadrenocorticism(pituitary- or adrenal-dependent), hyperaldosteronism, hypoadrenocorticism and adrenal neuroendocrinetumors.