The overall aim of the work outlined in this statement is to help establish a common framework for future scientific opinions dealing with the use of animal-based measures to assess the welfare of animals. The statement is mainly intended to support the work of EFSA, and a list of considerations for experts working on these future scientific opinions is presented. EFSA has already published a scientific opinion on dairy cattle and another on pigs related to the topic. This statement clarifies some common issues on terminology and integration of concepts, and presents some essential characteristics of animal-based measures to ensure that they are ‗fit for purpose‘. It highlights that more information is needed about the direction and strength of the various links between input factors and the animal-based measures (welfare indicators) that are used to assess their consequences. The statement highlights the importance of the systematic collection of standardised field data on animal-based measures and subsequent availability in well-defined databases. Targeted analysis of such data will help when selecting the most appropriate measure, or combination of measures, from the 'toolbox‘ of many potential measures, according to the specific purpose of the welfare assessment, as well as contribute to better assessing their validity and robustness. This will support the move towards quantitative risk assessment of animal welfare.