This paper provides a comparative analysis of assumptions and predictions of alternative economic theories of human aging and longevity. The Grossman (1972) model, which is based on the idea of health capital accumulation and the Dalgaard-Strulik (2014) model, which is based on the idea of health deficit accumulation. I show that both theories lead to fundamentally different predictions of health behavior and human life histories. I find that the Dalgaard-Strulik model provides a consistent approach to health behavior and aging whereas the Grossman model generates predictions that are hard to square with the stylized facts. I argue that root of this disagreement of the theories is the following: Grossman postulates that of two people of the same age the healthier one looses more health in the next instant whereas Dalgaard and Strulik, based on insights from modern gerontology, proceed from the opposite assumption.