The purpose of this study was to determine if a correlation existed between the classes of books checked out of the San Antonio College Library and the classes of books used in the Library. Data for out-of-library and in-library use were collected during February, 1978, and arranged by Dewey Decimal Classification (DDC) tens. By using the Pearson product-moment correlation formula, the author found a significant positive correlation between out-of-library and in-library use of books. It was also concluded that over-the-counter circulation count is a reliable indicator of total library use within the DDC tens class spans. (Author)