Selected free fatty acids (FFAs) are documented effective somatosensory and olfactory stimuli while gustatory effects are less well established. This study examined orthonasal olfactory, retronasal olfactory, nasal irritancy, oral irritancy, gustatory and multimodal threshold sensitivity to linoleic, oleic and stearic acids. Sensitivity to oxidized linoleic acid was also determined. Detection thresholds were obtained using a three-alternative, forced-choice (3-AFC), ascending concentration presentation procedure. Participants included 22 healthy, physically-fit adults sensitive to 6-n-propylthiouracil (PROP). Measurable thresholds were obtained for all FFAs tested and in 96% of the trials. Ceiling effects were observed in the remaining trials. Greater sensitivity was observed for multimodal stimulation and lower sensitivity for retronasal stimulation. There were no statistically significant correlations for linoleic acid thresholds between different modalities suggesting each route of stimulation contributes independently to fat perception. In summary, eighteen carbon fatty acids of varying saturation are detected by multiple sensory systems in humans