There is increasing evidence supporting an oral chemosensory detection system for free fatty acids (FFA). The presumptive transduction mechanisms have different ligand specificities. Psychophysical studies with FFA varying in chain length and saturation may aid in identifying the presence and functionality of these mechanisms in humans. Oral detection thresholds were measured for linoleic, stearic, lauric, and caproic acids in 32 healthy adults by an ascending, 3-alternative, forced-choice, sip and spit procedure. Thresholds were obtained for all fatty acids from all participants, but the distributions were wide and nonnormal. Thresholds were not correlated between fatty acids nor with thresholds for sucrose (taste), butanol (olfactory), mineral oil, or gum acacia (both somatosensory). These data demonstrate human oral sensitivity to short-, medium-, and long-chain FFA and suggest the presence of multiple transduction mechanisms. The findings are consistent with, but do not definitively demonstrate, a role for taste that may have a genetic basis.