This document provides guidance on drafting a Transboundary Diagnostic Analysis (TDA). It discusses integrating various parts of the TDA, such as thematic reports, studies, and stakeholder analyses. It recommends that a TDA should be concise and easy to understand, with an executive summary, main text, supporting data/figures, maps, a content list, and acknowledgements. Technical reports can be annexed. The TDA size typically ranges from 80-150 pages. Preliminary recommendations for the Strategic Action Program can be included. The TDA should be reviewed by stakeholders and adopted by the steering committee, though government acceptance is also often required.