The composition of the free fatty acid remaining in wool fabric that has been washed extensively in nonionic detergent solutions has been determined by thin-layer and gas chromatography. The acids are different from those of freshly secreted wool wax and contain straight-chain (64%, 10 members) and unsaturated (35.4%, 13 members) acids. The major acids are n-hexadecanoic (21. 3%), n-octadecanoic (33. 0%), and cis-DELTA9-octadecenoic (18%). No hydroxy acids are present. The origin of the acids has not been ascertained, but their composition and the treatment of the wool prior to the analysis preclude the possibility that they are suint components or soap products. By extracting the fabric with different solvents under controlled conditions, it has been shown that the lipid contaminant is situated both on the surface and inside the fiber.