The surface compositions, chemistry, and wettability of wool fiber fabrics in both native and UV-exposed states have been investigated, X-ray photoelectron spectroscopy shows surface oxygen levels of 10-12 at.% for native wool, which increase to as much as 27.5 at.% on UV exposure. Investigation of C1s and S2p photo-electron line energies shows this increase to be due largely to oxidative cleavage of native disulfide bonds to form sulfonic acid groups together with some formation of COOH/COOR on the wool fiber surfaces. A quantitative relationship is demonstrated between surface chemical states and water wettability.