Radionuclide imaging of endocrine diseases has been in clinical application for many years. Over the past six decades, an increasing number of radionuclides and radiolabeled compounds are available for imaging the endocrine organ/tissue functions. Radionuclide imaging provides functional as well as morphological information on multiple endocrine organs especially thyroid, parathyroid, and adrenal glands. Endocrine nuclear medicine includes not only diagnosis but also internal radionuclide therapy. Recently, radiolabeled peptides have also been used for diagnostic and for therapeutic purposes.