Volume 26 of the Journal will appear in two parts, of which this is Part 1, and will be devoted entirely to indexes covering Volumes 1–25. This part contains an Index of contributed papers, by authors (including problems); an Index of abstracts, by authors; an Index of reviews by authors (i.e., by authors of the works reviewed); and an Index of reviewers. It is planned to devote Part 2 to an Index of reviews by subjects — which, unlike the other indexes of reviews, will cover also the material in A bibliography of symbolic logic — and to a Chronological index of reviews, designed to supply in brief summary the actual bibliographical references for items which are reviewed or listed in the review sections of Volumes 1–25.