This document presents a set of Best Practice Guidelines for road development and rehabilitation in the Mekong floodplains of Cambodia and Viet Nam. The guidelines are developed under the ‘Roads and Floods’ project1. The guidelines are based on the review of local practice, international experience, and case study results. They are intended for use by professionals and organisations involved in road planning and design in the Mekong floodplains, as well as those involved in environmental and integrated assessments of road developments in the Mekong basin or structural developments in this basin in general. The Best Practice Guidelines are based on the case study results, the review of current international practice as well as the practice in the Mekong Basin. In the presentation of the Best Practice Guidelines, each of the recommendations is followed by an explanation including reference to their origin.More information on the ‘Roads and Floods’ project, its activities and results can be found in the Roads and Floods Synthesis Report. The set of Best Practice Guidelines for road development and rehabilitation in the Mekong floodplains of Cambodia and Viet Nam consists of the following three Best Practice Guidelines: - Best Practice Guidelines for Integrated Planning of Road Development and Rehabilitation. - Best Practice Guidelines for Environmental Assessment of Road Development and Rehabilitation. - Best Practice Guidelines for Technical Design of Road Development and Rehabilitation.