A survey of 301 Illinois special libraries was conducted in 1982 to determine the number and type of statistics collected by these libraries and the ways in which these data are used. The mean number of statistics collected was reported as 10, including both technical and public service measures. Measures kept regularly by at least 50% of the respondents included items received on interlibrary loan (ILL), periodical titles received, items cataloged, items sent on ILL, items received, items borrowed, items in collection, items ordered, and photocopies received. It was also reported that data collected were used for reports to management, financial and budgetary concerns, user and use analysis, collection analysis and inventory, reports to external agencies, personnel considerations, establishment of goals and objectives, and answering questionnaires. Data cross analyses were conducted by library subject area, the for-profit or not-for-profit status of the library's parent organization, size of primary clientele and library professional staff, and the level of management (middle or upper) to which the librarian reports. This document describes survey methodology and results and presents case studies concerned with the collection and use of statistical data in three special libraries. Appendices provide a sample questionnaire, eight reference tables, and a 16-item bibliography. (ESR)