With this issue, we inaugurate the weekly publication schedule for Physical Review Letters. We caution both our readers and our potential contributors that the present issue is considerably larger than they should expect on the average. The interval during which this material accumulated corresponded not only to the two weeks of 1963 remaining after the issue date of Vol. 11, No. 12-already twice what will be standard hereafter-but to an additional week arising from the accident of the calendar that the first Monday in 1964 is 6 January. We are convinced that the total number of Letters published per year should not increase significantly. Accordingly, the average number of Letters per issue should be only about half what it has been in the past. However, we hope to reduce somewhat the average delay between receipt and publication of acceptable Letters, and we are certain of a reduction in the delay between publication date and delivery of each issue.