Women were tested for sensitivity to several odorants at ovulation and menstruation. Three involatile esters (pentadecalactone, coumarin, and cinnamyl butyrate) predicted by gas chromatographic data to be strongly retarded by the olfactory mucus showed similar significant changes in sensitivity. By contrast, a more volatile ester (amyl acetate) predicted to diffuse more readily though the mucus showed no such changes. This suggests that variations in olfactory sensitivity observed between ovulation and menstruation depend on odorant volatility and thus may result from peripheral mechanisms limiting the access of odorant molecules to the olfactory receptors.