This paper provides an overview on the content of the ecoinvent database and of selected metholodogical issues applied on the life cycle inventories implemented in the ecoinvent database. In the year 2000, several Swiss Federal Offices and research institutes of the ETH domain agreed on a joint effort to harmonise and update life cycle inventory (LCI) data for its use in life cycle assessment (LCA). With the ecoinvent database and its actual data v1.1 a consistent set of more than 2'700 product and service LCIs covering the energy, transport, building materials, chemicals, pulp and paper, waste management and agricultural sectors is now available. Datasets are valid for European and Swiss conditions but partly also for other regions in the world (e.g., gas and oil extraction, metals mining). Nearly all process datasets are transparently documented on the level of unit process inputs and outputs. Methodological approaches have been applied consistently throughout the entire database content and thus guarantee for a coherent set of LCI data. This is particularly true for market and trade modelling, and for the treatment of multioutput and of recycling processes. Most multi-output processes are implemented as such, i.e., in their unallocated form with several co-product outputs and related allocation factors. With the help of these allocation factors, unit process raw data are derived and additionally stored in the ecoinvent database. This approach guarantees that 100 % of all inputs to and outputs from the multi-output process are allocated to the co-products. Transparency in reporting on a unit process level helps to adjust allocation factors applied on a multi-output process to one’s own needs. With limited own efforts one can even change the allocation approach from allocation to system expansion, in case this is considered more appropriate. Although measures have been taken to minimise errors in the database, they cannot be excluded. A pro-active information policy on data errors is followed. It helps the users to judge whether they may still work with the present version of ecoinvent data or they better correct selected errors that might otherwise influence the outcome of their current LCA case studies. The existence of the ecoinvent database proves that it is possible and feasible to build up a large interlinked system of LCI unit processes. The project work proved to be demanding in terms of co-ordination efforts and consent identification. One main characteristic of the database is its transparency in reporting to enable individual assessment of data appropriateness, to support the plurality in methodological approaches when using an ecoinvent dataset in another context and to allow for efficient and individual error corrections.