Photodynamic therapy is a relatively new treatment for superficial squamous cell carcinoma in cats. There are no publications indicating that the method is being used in veterinary practice in Sweden at the present time. The method uses the interaction between a photosensitive agent which has been administered to the tumor area, light of a wavelength that can be absorbed by the photosensitiser and the presence of oxygen. In this study photodynamic treatments were performed at the Queen?s Veterinary School Hopital of Cambridge University between 1998 and 2002.