In this study designed to determine the use of U.S. public and academic libraries, data was obtained by a review of the pertinent literature, a nation-wide public opinion poll, and a survey of a selected group of library experts. Only 11 pertinent published studies were found. Of these nearly half are limited to use of academic libraries, there is very little on reasons for non-use, and Berelson's 1949 study is still the most comprehensive. The national social survey of adult attitudes towards libraries, administered by the Gallup Organization, found that the adult public library clientele is primarily upper middle class, and the actual current adult clientele is only half the number of potential adult users. Library experts felt that personnel is the most critical problem, that automation and better utilization can contribute most to improvement of library operations, and libraries do better with traditional functions than with meeting new opportunities and the needs of the modern urban community. It is recommended that libraries undertake an intensive self-examination of objectives and target publics and that a national library usage research body be created. Appended is an 11 item bibliography, the opinion poll responses, and the survey questionnaire. This study was originally submitted under the title "Public and Academic Library Usage in the United States." (JB)