The 1948 edition of the United States Air Force Statistical Digest has been segregated into two separate volumes. Volume I contains statistical data which are classified "Restricted " or are unclassified, whereas Volume II includes information classified as high as "Secret." This publication represents the latter of the two volumes. The greater portion of the information included in this volume had been classified no higher than ''Restricted" in previous editions of the Digest. The change in the classification of this mater was made after a security survey, completed during the early part of the year, indicated that the classification of such information should be raised, due to the current relative importance of this type of data to national security. Another change, made effective with the 1948 edition of the Digest, pertains to the scope of the data included in much of the statistical tables. Although it includes the majority of the tables carried in the 1947 edition, the present issue is unlike that for previous years in that its coverage has been restricted to data for the Calendar Year 1948. In addition several new tables have been added.