Under the UNEP-SETAC Life Cycle Initiative the six most commonly used characterization models for toxic impacts from chemicals were compared and harmonized through a sequence of workshops removing differences which wereunintentional or unnecessary. A parsimonious (as simple as possible but as complex as needed) and transparent consensus model, USEtox, was created producing characterization factors that fall within the range of factors from the harmonised existing characterisation models. The USEtox model together with factors for several thousandsubstances are currently under review to form the basis of the recommendations from the UNEP-SETAC Life Cycle Initiative in this field.