Two key types of well–being, eudaimonic and hedonic, are reviewed. The first addresses ideas of self–development, personal growth and purposeful engagement, while the second is concerned with positive feelings such as happiness and contentment. How well–being varies by age and socio–economic standing is briefly summarized, followed by examination of its biological correlates (neuroendocrine, immune, cardiovascular, rapid eye movement (REM) sleep). Preliminary findings on a sample of ageing women showed that those with higher levels of eudaimonic well–being had lower levels of daily salivary cortisol, pro–inflammatory cytokines, cardiovascular risk, and longer duration REM sleep compared with those showing lower levels of eudaimonic well–being. Hedonic well–being, however, showed minimal linkage to biomarker assessments. Future research directions building on these initial findings are discussed.