Volume 10 of the Series contains the consensus document on the “Environmental Considerations for Risk/Safety Assessment for the Release of Transgenic Plants” developed by the OECD Working Party on the Harmonisation of Regulatory Oversight in Biotechnology. Transgenic plant varieties are subject to official risk/safety assessment, science-based and case-by-case, before their potential release into the environment. The document contains general information on environmental risk/safety assessment, its key concepts, structure and planning. Annexes describe seven examples of environmental considerations routinely examined by assessors and taken from experience gained during such assessment: Invasiveness and weediness; Vertical gene flow; Organisms (animals); Soil functions; Plant health; Crop management practices; and Biodiversity (protected species and habitats/ecosystems). The purpose of this document is not to elaborate new terminology or to describe how to undertake an actual risk/safety assessment, but rather to outline an approach and provide illustrative examples for helping assessors in planning and structuring an environmental risk/safety assessment. This document should be of interest to regulators and safety assessors, as well as to plant breeders and the wider scientific community. More information, including other tools for environmental risk/safety assessment such as OECD consensus documents on the biology of crop species, are found at BioTrack Online.