In alternating years, the Denver X-ray Conference turns its principal attention, through the choice of subjects for the plenary lectures, to various aspects of either X-ray fluorescence or dif­ fraction. This is a "fluorescence" year, and the three invited lecturers are experts in techniques that are at, or perhaps yet a bit beyond, the forefront of our understanding and technology in that field. The common denominator in selecting these subjects was that each is approaching a full elucidation of theory, and active develop­ ment of practical hardware, and that each presents analytical pos­ sibilities which can hardly be ignored in the next generation of commercial instrumentation. In other words, these are techniques that many of us shall likely find ourselves using by the end of the decade. The greatest difficulty in selecting the subjects was the need to overlook others, particularly 1) the increasing inter­ est in "in-situ" or on-line analytical control, for tagging, identi­ fication or sorting; and 2) the broad subject of the computeriza­ tion of instrumentation, with its powerful impact on the design of hardware, and its open invitation to the theorist to create more exact mathematical models of the analytical process, regardless of complexity, in the expectation that programmers will find ways to implement solutions in affordable, dedicated computers.