This article explores three potential existential contributions to an evolving theory of human lifestyles. Following a brief review of the impact existential psychology has had on current thinking in the behavioral sciences, the three Cs of lifestyle theory-conditions, choice, and cognition-are discussed with respect to several key existential concepts, most notably, existential fear, intentionality, and the power of nonempirical thought. It is argued that the continued viability of existential psychology and lifestyle theory rests with their ability to generate concepts and hypotheses not readily available from more currently popular behavioral science theories.