This is the fourth guidance note in a four-part series of notes related to impact evaluation developed by InterAction with financial support from the Rockefeller Foundation.This fourth guidance note, Use of Impact Evaluation Results, highlights three themes crucial for effective utilization of evaluation results. Theme one states that use does not happen by accident. Impact evaluations are more likely to be used when uses have been anticipated and planned from the earliest stages of the evaluation and, even better, from the planning stages of the work that is being evaluated. Theme two concerns the operations and systems required in an organization to use impact evaluations well. Theme three builds from the premise that the first two themes are necessary but insufficient conditions for the effective and widespread use of impact evaluations. The guidance note is also available in French, Arabic and Spanish on https://www.interaction.org/impact-evaluation-notes.