Radiohalogens play a very important role in radiopharmaceuticals used for medical imaging (now referred to as molecular imaging) and therapy applications. Development of new radiopharmaceuticals that have radiohalogens incorporated requires an understanding of parameters that are unique to chemistry involving these radionuclides. Those parameters include requirement for production and purification of the halogen radionuclides, as well as development of reaction conditions for use with high specific activity short-lived radionuclides. In this tutorial review, several radiohalogens, their radiolabeling chemistry and their application to medical imaging and therapy are discussed.