What has happened to the nuclear medicine subspecialty since those earlier issues of the Seminars in Nuclear Medicine? The earliest issues in 1972 presented topics in vogue at the time that included brain "scanning," cisternography, whole body counting, and abdominal imaging with (99m)Tc pertechnetate. The second pediatric subspecialty issues in 1993 reflected a 21-year evolution of the subspecialty and included the topics of renal scintigraphy, labeled cells for abdominal imaging, metaiodobenzylguanidine imaging, single photon emission computed tomography, and bone scintigraphy for benign disorders. The current issues will address diverse topics that cover the spectrum of the current practice of pediatric nuclear medicine. They include radiation exposure and absorbed dose reduction, positron emission tomography/computed tomography in children, neuroblastoma and other neuroendocrine tumors, thyroid cancer and therapy, bone density studies and, of course, the most prevalent studies in children, renal and bone. Brain, heart, and lung studies complete the spectrum.