The idea for the present Spilite Volume was born during the Spilite Symposium at the XXIIIrd session of the International Geological Con- gress in Prague, 1968. At that time, only a restricted number of petro- logists working on spilites was present and, therefore, the group assem- bled agreed that a Symposium Volume should also include recent papers by many other spilite specialists. At the same time it was agreed that the papers presented at the Symposium should be returned to the authors for changes and additions. This procedure of upgrading and amending the papers has continued until this year (1973) for various technical and editorial reasons. The information presented here is, therefore, up-to- date. To those familiar with the spilite problem it is obvious that the time had come for a review of its state. Also, the existing litera- ture had become so voluminous that a monographic review was necessary. Following a modern trend, the authorship for this review was spread among specialists with variable experience. For readers not necessarily familiar with the spilite problem, a brief summary is presented here. A short historical note is followed first by the observations, then by the interpretations, finally by some of the major features of scientific logic as they pertain to the problem of the primary or secondary origin of some of the rocks termed spilites and keratophyres.