This paper reviews and summarizes the procedures used by the Library Research Center (LRC) of the University of Illinois to process data from Illinois public library annual reports filed with the Illinois State Library (ISL). The complete processing cycle is described, including: (1) preparation and revision of reporting forms; (2) their distribution and review; (3) the coding of data and its input into a computer file; (4) error checks performed; and (5) the generation of products, particularly a set of information elements from each library which is published annually in "Illinois Libraries," and the annual "Analyses of the Illinois Public Library Statistics," which presents sixteen ratios and percentages derived from annual report data. Information on processing costs and samples of input, editing and output programs are also provided. (ESR)