On two previous occasions, we have felt the necessity of restricting publication of Letters pertaining to some particular topic. The previous topics were masers1 and the Mössbauer effect.2 We believe that the same sort of situation has arisen again. This time the topic is internal symmetries. As was recognized on the other occasions, a new discovery "naturally inspires much research resulting in papers `of high current interest' suitable for publication in Physical Review Letters."1 Eventually, however, a stage is reached in which the major implications of the new development have been recognized, and there remains only routine elaboration. In our judgment, the area of unitary symmetries-SU(6), Ũ(12), W(6), and the like-has now reached such a stage. Hereafter, papers in this area will be considered only if they propose a genuinely new concept which makes possible the correlation of previously unrelated data. When we think about it, we believe that would not be a bad criterion to apply to every theoretical paper submitted as a Letter!