Variation in the form, pattern and pace of ageing is studied by scientists in multiple disciplines and there is much to be gained from more cross-disciplinary communication. This chapter suggests here that the framework provided by Tinbergen’s ‘Four Questions’ is useful in integrating ageing research. It emphasizes the need to separate biological and chronological age and describe several markers of age-related deterioration that could be used more widely to measure biological age, with a focus on those that can be deployed outside of the standard laboratory setting and be used repeatedly in individuals to enable longitudinal studies. Whole organism frailty measures are currently little used by evolutionary ecologists and this chapter describes how these could be used more extensively. Telomere attrition and mitochondrial function are highly conserved processes and have been studied in an increasingly wide range of taxa in recent years. The chapter also discusses other markers, including those related to immune function, oxidative damage, inflammation and DNA methylation. Great progress is currently being made in the use of epigenetic alterations to provide information on chronological and biological age in a range of (predominantly) vertebrate taxa. The chapter outlines how this integrative approach could be developed further and highlight future directions.