This Cumulative Index is intended to provide ready reference to all material published in the "American Journal of Physics" in Volumes 1 (1933) to 20 (1952). The Index is subdivided into two parts: an Author Index listing the names of the contributors of papers, notes, letters, book reviews, and abstracts of addresses; and an Analytical Subject Index listing the titles of papers, notes, letters, book reviews, addresses, and digests of periodical literature. The Author Index lists the names of contributors alphabetically; the Analytical Subject Index lists the titles of contributions according to a Classification of Subjects to be found on page 2 of this Index.