This manual is a first effort to begin to identify, describe, and develop procedures for assessing various aspects of digital reference service. Its overall purpose is to improve the quality of digital reference services and assist librarians to design and implement better digital reference services. More specifically, its aim is to: assist librarians and others to develop ongoing programs of assessment of digital reference services; provide a practical set of guidelines and procedures for how assessment of digital reference services can be done; and develop standardized procedures and definitions of statistics and measures that may be compared across different libraries. The first chapter is an introduction that provides a short background discussion on digital reference service, outlines the need for digital reference evaluation, and describes the purpose and format of the manual. The second chapter describes the various statistics and measures selected for inclusion in this manual. The chapter is divided into the following sections: Descriptive Statistics and Measures; Log Analysis; User Satisfaction Measures; Cost; Staff Time Expended; Other Assessment Options; and Quality Standards. Each statistic and measure is described in terms of these general categories: Definition, Rationale, Data Collection Procedures, and Issues and Considerations. Appendixes include sample forms, reports, logs, worksheets and survey instruments; and other statistics and measure considered for the manual. (Contains 14 references.) (AEF)