The effect of water vapour plasma treatment on the shrinkage behaviour and chemical properties of the surface of keratin fibres was studied. The wettability and shrink resistance of wool were improved even at low plasma treatment times. The values of the advancing contact angles of keratin fibres treated with plasma provide evidence of the formation of hydrophilic groups in the wool surface. Analysis by XPS reveals that oxidation of the fatty acid monolayer (F-layer) prevails over its removal in the early stages of plasma treatment. The increase in treatment time results in a progressive removal of the F-layer.