Ageing is a physiological process that is part of normal development (Cutler, 1991). However, the stress response in humans, although an adaptive mechanism initially, has the potential to be chronic and detrimental to the organism if too large and/ or prolonged (Sapolsky, 2007). This particularly appears to be the case later in the lifespan; in fact some of the changes in older age mirror the chronic effects of stress on several of the body’s biological systems. This chapter will mainly focus on the impact of stress on the immune system and the implications for resilience in older age, as stress effects on all bodily systems are beyond the scope of one chapter. Further, the immune system undergoes several changes with ageing, resulting in increased susceptibility to infectious and autoimmune diseases and cancer, all of which are also influenced by stress.