This training kit presents the central messages of Life Cycle Assessment (LCA) in a format accessible to a diverse  set of target audiences, starting with  decision-makers, policy officials, business managers and then progressing towards those who will be active in performing LCAs as well as those who wish to understand the many and finer details of LCA. The training kit explains LCA under four main topics: (1) Introduction to LCA and its relation with environmental decision support; (2) Overview of LCA; (3) In-depth presentation of the main issues in LCA; (4) Specialization modules for selected topics. Each topic is composed of a set of training materials and the kit is also supplemented by a training manual and a set of reference materials.