Prevalent beliefs in both scientific and popular culture are 1) humans have a poor sense of smell, and 2) smell plays a minimal role in social behavior. However, this consensus is shifting with researchers even suggesting olfaction influences mate choice. Still, studies of odor-based communication in humans remain inconclusive because of poorly designed experiments, scant replication studies, and publication bias. Thus, the goal of this dissertation was to return to first principles and build a solid foundation for the study of human olfaction and mate choice. Chapter 1 provides a rich overview of human olfaction and odor-based communication, revealing the poor methods used in studies of pheromones and body odor. Chapter 2 investigates the impact of a putative female pheromone, copulin, on men’s mating psychology, using rigorous methods (e.g., a placebo-controlled, odor-masking design) and a large sample (n = 243 men). The findings reveal that when the limitations of prior pheromone research are addressed, there is no evidence that copulin is a pheromone. Chapter 3 asks whether some individuals smell more or less attractive to the opposite sex. Studies of mate choice from an evolutionary perspective often begin by investigating whether individuals of one sex agree on the attractiveness level (e.g., facial attractiveness) of individuals of the opposite sex. For comparison, a uniform methodology was used to assess agreement in judgments of physical and vocal attractiveness, modalities in which evidence of shared preferences is generally accepted. No differences were discovered between modalities. Therefore, to the extent shared preferences exist for faces and voices, there is also evidence of shared preferences for body odors. Chapter 4 examines the relationships between independent multisensory judgments of attractiveness (i.e., face, voice, and body odor attractiveness). For men, modalities of attractiveness did not covary. However, in women results indicate weak covariances between all modalities. Moreover, a latent general attractiveness factor (i.e., common fitness correlate) modestly contributed to covariances between modality-specific attractiveness. Together, these findings suggest historical views of human olfaction as unimportant were misguided. In fact, the evidence demonstrates body odor plays a similarly important role to physical and vocal attraction in human mate choice.