Analysis of Competing Hypotheses (ACH) is a simple model for how to think about a complex problem when the available information is incomplete or ambiguous, as typically happens in intelligence analysis. The software downloadable here takes an analyst through a process for making a well-reasoned, analytical judgment. It is particularly useful for issues that require careful weighing of alternative explanations of what has happened, is happening, or is likely to happen in the future. It helps the analyst overcome, or at least minimize, some of the cognitive limitations that make prescient intelligence analysis so difficult. ACH is grounded in basic insights from cognitive psychology, decision analysis, and the scientific method. It helps analysts protect themselves from avoidable error, and improves their chances of making a correct judgment.