This report provides an operational guide to the ISO standards for Life Cycle Assessment (LCA). It was prepared by a team of researchers from various institutions in the Netherlands and Denmark, including the Centre of Environmental Science - Leiden University (CML), the Fuels and Raw Materials Bureau (Bureau B&G), and the Delft University of Technology. The study was commissioned by several Dutch ministries, including the Ministry of Housing, Spatial Planning and the Environment (VROM-DGM), the Ministry of Economic Affairs (EZ), the Ministry of Agriculture, Nature Management and Fisheries (LNV), and the Ministry of Transport, Public Works and Water Management (V&W). The report was developed through collaboration with multiple organizations, including the Institute for Environmental Studies - Vrije Universiteit (IVM), the School of Systems Engineering, Policy Analysis and Management – Delft University of Technology (TUD/TB), and the Netherlands Organisation for Applied Scientific Research (TNO). The report outlines the main characteristics of LCA, its role in product and wider applications, and its limitations. It discusses the international developments in LCA, including the role of SETAC, ISO, and UNEP. The report also provides guiding principles for the present Guide, emphasizing the need for up-to-date science, operationalization of ISO standards, and relevance to various applications. The Guide is divided into three parts: Part 1 provides an introduction to LCA, its purpose, and background; Part 2 includes a Guide and an Operational Annex; and Part 3 provides the scientific background for the guidelines. The report also includes a reading guide, explaining the structure and purpose of each part. The report emphasizes the importance of LCA as a tool for environmental management and decision-making, and highlights the need for further development and application of LCA in various contexts.This report provides an operational guide to the ISO standards for Life Cycle Assessment (LCA). It was prepared by a team of researchers from various institutions in the Netherlands and Denmark, including the Centre of Environmental Science - Leiden University (CML), the Fuels and Raw Materials Bureau (Bureau B&G), and the Delft University of Technology. The study was commissioned by several Dutch ministries, including the Ministry of Housing, Spatial Planning and the Environment (VROM-DGM), the Ministry of Economic Affairs (EZ), the Ministry of Agriculture, Nature Management and Fisheries (LNV), and the Ministry of Transport, Public Works and Water Management (V&W). The report was developed through collaboration with multiple organizations, including the Institute for Environmental Studies - Vrije Universiteit (IVM), the School of Systems Engineering, Policy Analysis and Management – Delft University of Technology (TUD/TB), and the Netherlands Organisation for Applied Scientific Research (TNO). The report outlines the main characteristics of LCA, its role in product and wider applications, and its limitations. It discusses the international developments in LCA, including the role of SETAC, ISO, and UNEP. The report also provides guiding principles for the present Guide, emphasizing the need for up-to-date science, operationalization of ISO standards, and relevance to various applications. The Guide is divided into three parts: Part 1 provides an introduction to LCA, its purpose, and background; Part 2 includes a Guide and an Operational Annex; and Part 3 provides the scientific background for the guidelines. The report also includes a reading guide, explaining the structure and purpose of each part. The report emphasizes the importance of LCA as a tool for environmental management and decision-making, and highlights the need for further development and application of LCA in various contexts.