The low-molecular weight organic constituents of human vaginal secretions from normally cycling subjects were analyzed both before and after sexual stimulation. Gas chromatography and combined gas chromatography-mass spectrometry were employed in the analyses of the secretions. Consistent increases were noted for a number of the lipid constituents of the secretions, suggesting that they are derived at least in part from the plasma and transude into the vaginal lumen during arousal. In addition, the increases in the concentrations of glycerol and stearic acid with respect to baseline levels were significant (P is equal to and less than 0.05). Compounds which are produced intravaginally appear to decrease in concentration during the arousal interval because of dilution by the transudate. No consistent qualitative changes were noted in the secretion.