This article describes a web-based computer-assisted tool for diagnosing progress in international negotiation. Following a discussion of the need for such a tool, we provide the research sources for its development, present the model on which it is based, describe how it works, and present the results of attempts to validate its diagnoses with case materials. Focusing on flexibility in negotiation, the program consists of questions divided into five categories: issues, parties, delegations, situation, and process. The questions track to variables shown in published studies to influence flexibility. Answers to the questions are processed according to algorithms that include weights derived from the results of a statistical meta-analysis of bargaining studies. An example of the question-answer format and computations leading to the diagnoses are provided. A help function that provides advice for resolving impasses is also described. Strong correspondences between diagnoses generated by the program and actual outcomes obtained in a number of cases attest to the validity of the approach. The article concludes with ideas for further development stimulated by the web-based version of the program.