The result of a pilot study funded by the Library Services and Construction Act (LSCA), this document is both a report of a test of adaptations of "Output Measures for Public Libraries" for the measurement of children's services in Wisconsin public libraries, and a manual for children's librarians to use for future data collection. The material is intended to supplement "Output Measures for Public Libraries: A Manual of Standardized Procedures" (Zweizig and Rodger, 1982), and the numbers of the measures and page number references refer to that document. Measurement issues and sample sizes are discussed, and a three-phase pattern for gathering information is provided. Reports are then presented on the following measures used in this project: (1) Measure 1--Juvenile Circulation per Juvenile Capita; (2) Measure 2--In-Library Use of Juvenile Library Materials per Juvenile Capita; (3) Measure 3--Juvenile Library Visits per Juvenile Capita; (4) Measure 4--Annual Juvenile Program Attendance per Juvenile Capita; (5) Measure 6--Reference Fill Rate for Juveniles; (6) Measure 10--Library Registration of Juveniles as a Percentage of Juvenile Population; and (7) Measure 11--Turnover Rate of Juvenile Materials. Samples of forms used in the study are provided, including summary sheets for recording data on elements and output measures, and for reporting the collection experience. Additional data are summarized in three tables. (KM)