THIS ISSUE PAPER IS THE FIRST OF SIX PRODUCTS OF A NATIONAL EVALUATION OF PRETRIAL RELEASE PROGRAMS TO DETERMINE THE CURRENT KNOWLEDGE OF THEIR EFFECTIVENESS, TO ASSESS THE USEFULNESS OF THIS KNOWLEDGE FOR PLANNING AND FUNDING DECISIONS, AND TO DEVELOP RESEARCH DESIGNS TO OBTAIN INFORMATION NECESSARY FOR A FULL EVALUATION. THE NEED FOR REFORM IN AMERICAN PRETRIAL RELEASE PRACTICES AND A BRIEF OVERVIEW OF THEIR DEVELOPMENT ARE INCLUDED AS WELL AS A DEFINITION OF THE CONCEPT AND A DISCUSSION OF FUNDAMENTAL SIMILARITIES AND DIFFERENCES AMONG THE PROGRAMS. EXISTING RESEARCH IS CONSIDERED AND VARIOUS APPROACHES TOWARD EVALUATING PROGRAM EFFECTIVENESS ARE IDENTIFIED. AN ASSESSMENT OF THE CURRENT STATE OF KNOWLEDGE CONCERNING PRETRIAL RELEASE PROGRAMS IS ALSO PRESENTED. FOR THE OTHER FIVE PARTS OF THIS PHASE I EVALUATION, SEE NCJ-32739-43.