Nuclear Medicine and Biology publishes original research covering all aspects of radiopharmaceutical chemistry: synthesis, radiopharmacy, in vitro and ex vivo testing, and in vivo evaluation of molecular probes for PET,SPECT, planar imaging, and autoradiography. These multidisciplinary studies should demonstrate the mechanism of localization whether the radioactive substance is based on receptor, enzyme, tumor antigen, or other well-defined biochemistry. The study should also address the sensitivity of the probe to changes in biochemistry, although studies of mechanism alone are acceptable. Contributions on the subject of therapeutic radiopharmaceuticals also are appropriate provided that the specificity of labeled compound localization and therapeutic effect have been addressed. If the synthesis of a new radiopharmaceutical is submitted alone, then the uniqueness of the chemistry must be emphasized. Papers that describe instrumentation important to molecular imaging as well as papers describing translational clinical research and the issues of extending preclinical research to clinical studies are also welcome.