A detailed study of the alkaline degradation of PVdF has been carried out by X-ray photoelectron spectroscopy, secondary ion mass spectrometry and Raman spectroscopy to determine the composition of the modified layer. The study indicates the formation of a surface layer consisting of conjugated C=C bonds and the inclusion of oxygen functionalities on treatment. A mechanism for this degradation process is proposed. This includes the formation of the polyene structure followed by hydroxide attack to yield hydroxyl and carbonyl groups.