This study was designed to inform the development of a national joint prison-probation service assessment instrument. It focuses on two assessment instruments, the ACE (Assessment, Case Management and Evaluation) and the LSI-R (Level of Service Inventory - Revised). The research addressed probation officers' and middle managers' use of these instruments and their perceptions of them. Researchers interviewed 21 senior probation officers and 50 probation officers, including 18 ACE and 22 LSI-R users, in 10 probation service jurisdictions. The focus of the interview was on the extent of the use of the assessment instruments and users' views of the strengths and weaknesses of the tools. The study concludes that assessment tools were widely used and performed a variety of functions, including assisting in the production of pre-sentence reports and completing supervision plans. Overall, the use of a standardized assessment tool was viewed by the respondents as being useful in assisting the work of probation staff. This report also summarizes particular benefits and limitations of each of the instruments and offers recommendations for the development and implementation of a national assessment instrument. 12 tables, appended interview questions, and 7 references