Many species use olfactory signals to assess potential social and sexual partners. Although some of the information encoded in odorants may be static (e.g., individual or kinship signatures), semiochemical profiles also vary with changing circumstances (e.g., dietary or seasonal variation). The ring-tailed lemur (Lemur catta), a strepsirrhine primate endemic to Madagascar, provides a unique model for examining the complex interaction between changing physiological conditions and the communication of static information. Through behavioral assays, genetic profiling, and chemical analyses, we have shown that lemur scent secretions encode honest and discernible information about identity, sex, reproductive status, genetic quality (i.e., heterozygosity), and pairwise relatedness among conspecifics. Using a combination of natural experiments and controlled endocrine manipulations, we explore the hormonal mediation of these scent signals: specifically, we link variation in female reproductive hormones to variation in female semiochemical expression. We have found that changes in the chemical composition of odorants parallel changes in endocrine function associated with seasonal breeding, different stages of pregnancy, and the administration of hormonal contraceptives. These studies reveal that even moderate changes to endocrine profiles can dramatically alter lemur semiochemical profiles and the information they encode.