We review research on physiological correlates of volunteering, a neglected but promising research field. Some of these correlates seem to be causal factors influencing volunteering.Volunteers have better health, both self-reported and expert-assessed, and perform better on In what way could the physiology of volunteers be different from non-volunteers? We discuss six groups of physiological correlates: in the areas of health, cognition, neurology, hormones, and genetic factors. The chapter is written from a growing awareness that most of the research on volunteering in the social sciences has ignored physiological aspects of human