Abstract: Environmental implications of the whole supply-chain of products, both goods and services, their use, and waste management, i.e. their entire life cycle from "cradle to grave" have to be considered to achieve more sustainable production and consumption patterns. In the Communication on Integrated Product Policy (IPP), the European Commission committed to produce a handbook on best practice in Life Cycle Assessment (LCA). The Sustainable Consumption and Production (SCP) Action Plan (EC, 2008) confirmed that "(…) consistent and reliable data and methods are required to assess the overall environmental performance of products (…)". In this context, JRC led a "science to policy" process which resulted in the ILCD International Reference Life Cycle Data System (ILCD) Handbook ILCD Handbook is a series of detailed technical documents, providing guidance for good practice in Life Cycle Assessment in business and government, serving as. "parent" document for developing sector- and product-specific guidance documents, criteria and simplified tools. For Life Cycle Impact Assessment (LCIA), the Handbook provide guidelines to methods and assessments to analyse the emissions into air, water and soil, as well as the natural resources consumed in terms of their contributions to different impacts on human health, natural environment, and availability of resources. Several methodologies have been developed for LCIA and some efforts have been made towards harmonisation. In order to support the selection of the methods, criteria for good characterisation modelling practice were developed in advance to be used in the evaluation and comparison of the selected methods. The criteria include scientific, applicability and stakeholder acceptance issues. Methods and models for LCIA were reviewed, covering different impact categories such as climate change, ozone depletion, photochemical ozone formation, respiratory inorganics, ionising radiation, acidification, eutrophication, human toxicity, ecotoxicity, land use and resource depletion. The guidelines for LCIA come from a comprehensive process of selection of methods based on a set of scientific and stakeholder acceptance criteria and involving extensive hearings of domain experts, advisory groups and the public, during a public consultation. In this "from science to policy support" process a number of research needs, critical issues and challenges for Life Cycle Impact Assessment emerged. Robustness of models and reliability of characterisation factors must be the basis for further development in Life Cycle Impact Assessment (LCIA).