The article by Ryff, Singer, and Love explores the relationship between well-being and biological health, focusing on two key types of well-being: eudaimonic and hedonic. Eudaimonic well-being is associated with self-development, personal growth, and purposeful engagement, while hedonic well-being is linked to positive feelings and happiness. The authors review the socio-demographic correlates of these two types of well-being and examine their biological correlates, including neuroendocrine, immune, cardiovascular, and sleep systems. Preliminary findings from a sample of aging women show that those with higher levels of eudaimonic well-being have lower levels of daily salivary cortisol, pro-inflammatory cytokines, cardiovascular risk, and longer duration REM sleep compared to those with lower levels of eudaimonic well-being. Hedonic well-being, however, showed minimal linkage to biomarker assessments. The authors discuss future research directions, emphasizing the need for longitudinal studies and the integration of eudaimonic and hedonic well-being in national health statistics.The article by Ryff, Singer, and Love explores the relationship between well-being and biological health, focusing on two key types of well-being: eudaimonic and hedonic. Eudaimonic well-being is associated with self-development, personal growth, and purposeful engagement, while hedonic well-being is linked to positive feelings and happiness. The authors review the socio-demographic correlates of these two types of well-being and examine their biological correlates, including neuroendocrine, immune, cardiovascular, and sleep systems. Preliminary findings from a sample of aging women show that those with higher levels of eudaimonic well-being have lower levels of daily salivary cortisol, pro-inflammatory cytokines, cardiovascular risk, and longer duration REM sleep compared to those with lower levels of eudaimonic well-being. Hedonic well-being, however, showed minimal linkage to biomarker assessments. The authors discuss future research directions, emphasizing the need for longitudinal studies and the integration of eudaimonic and hedonic well-being in national health statistics.