This document was initiated as a follow-up of a workshop jointly organised by the Working Group on Drainage (WG-DRG) and the Working Group on Performance Assessment (dissolved in 2003) in Cairo in 1996. A first draft was produced and presented at the ICID in Montreal 2002 and both from Australia and the USA additional contribution were received. A paper was presented in a special Benchmarking workshop held at the ICID meetings in Montpellier 2003. In 2005 it was decided to prepare a final version of the document with the assistance of CSIRO, Land and Water, Griffith, Australia. Case studies available up to this point have been included in this final version of the report. The authors wish to thank all members of the WG-DRG and those of Task Force 4 (20002004) of ICID on Benchmarking of Irrigation and Drainage Projects for sharing their observations and remarks. Performance assessment is not common in the drainage sector mainly because no comprehensive method has been developed so far. This document aims at partly filling this gap. It firstly explains the rationale and the basic concepts associated with performance assessment and then propose methods for performance assessment. It finally shows the rare case studies that are available, which are used to compile the inventory of the Performance Assessment programmes installed throughout the world. The document is a state of the art document, it is not definitive and might be considered as a first step on the path of incorporating drainage benchmarking into irrigation benchmarking. At the same time there will always be room for independent drainage assessment at farm and regional levels. Unaffordable methods such as information management systems, readily available geographical information systems and satellite remote sensing techniques will become more and more applicable in the forthcoming years. Because of this expected progress and because more case studies will become available, the task force who have prepared this document would like to see it as a first volume of Drainage Performance Assessment and Benchmarking. As new information becomes available, an additional volume may be considered. This report is divided into two parts; Part A describes performance assessment approaches, assessment parameters, indicators and criteria and discusses the role of benchmarking, whilst Part B provides practical case studies from Pakistan, Egypt, Morocco, France and Australia.