SummaryAlthough the last two decades has seen a keen interest in using supercritical fluids as media for material processing and chemical reactions owing to their unique physical properties, this technology has been underutilized in medical radioisotope processing and chemistry. The successful application of this technology necessitates not only having a sound knowledge of the physicochemical properties and phenomena occurring within such critical states of matter, but also a clear idea of the tools needed and means for applying them. These topics will be presented under the cover of two parts. Part I will address topics on the general background of supercritical fluid technology, equipment needed, whether for chemistry or separation, and basic techniques to access critical states of matter. Part II will follow in a subsequent volume and is meant to provide a description of applications with cited examples and potential areas for development. The hope is that sufficient interest is stimulated so as to encourage radiochemists to look to alternative technologies of this nature to