The field of diagnostic nuclear medicine has changed significantly in the past decade. Peptides have become powerful imaging agents for studying biochemical processes. The glucose analogue FDG has entered clinical routine, and significantly advanced the field of diagnostic oncology. There have been important improvements in instrumentation The enormous progress in computer speed has made it possible to implement better reconstruction algorithms, automate processing, and improve quantification. High-quality emission tomography with positrons will soon be the routine in our image armamentarium. The limitless number of tracers that can be used for further and deeper in-vivo exploration of processes in the human body. Molecular biology is being incorporated into nuclear medicine imaging, and the principles of gene imaging and specific applications are dealt with in this volume. The present text is an adjunct to the rapidly expanding knowledge in diagnostic nuclear medicine and attempts to provide both the student and the professional with an update of the developments in the last decade.