The symposium on Angiography/Scintigraphy brought to Mainz in the fall of 1970 not only many European colleagues with an interest in these techniques, but also a number of visitors from overseas. These busy, work-filled days are beginning to fade in the memory of those who were there. Nevertheless, the scientific results reported on that occasion still supply the guidelines for what is currently being done in radiology and nuclear medicine. Anyone who has kept abreast of the literature over the past few years will have noted with some surprise how comparisons of the results obtained with these two important diagnostic aids continue to provoke controversy. One thing is certain: the emblem chosen for the Mainz symposium could hardly have been more appropriate. Like two cogwheels meshing in some complex piece of machinery, these radiological procedures demand the highest level of skill and precision before they will function properly on engaging so as to produce optimal results. Their findings complement each other in almost ideal fashion. Even though development in these two diagnostic disciplines has not exactly stood still since 1970, the papers given at this symposium established the fundamentals from which have stemmed many an intelligent adaptation of a method, many a cunning modification of an instrument and, not least, many a new research lead. This is why we applaud the initiative of Professor Diethelm of Mainz, whose brainchild this symposium was, in making the proceedings available to a wider audience.