This chapter reviews the structures and abundances of the chemical compound groups reported in J. T. Knudsen et al. and discusses various aspects of variation in floral scent chemistry. Many floral scent compounds are chiral molecules with one or more asymmetric carbons. Enantiomers have identical values for all physical constants except that they interact with plane-polarized light in opposite directions. Floral scent production and composition is genetically determined but environmental factors may also exert a great impact on the scent emitted. Floral scent emission may vary in time because emission follows a circadian rhythm or external stimuli such as light or temperature. The primary function of floral scent in flowering plants is to attract and guide pollinators. The composition of floral scent varies both quantitatively and qualitatively at many different levels of organization. Knowledge of the chemistry of floral scents is critical in understanding their evolution and biological function.