They are definitely not purebred, just crosses. Here in New Zealand, the guide dog organisation I volunteer for has recently bred their first Golden Retriever/German Shepherd cross. It only resulted in one puppy but he is a cutie! The goal is to produce a guide dog that has the willingness and intelligence of the German Shepherd combined with the less energetic and non-foodiness and aloofness of the Golden Retriever. Time will tell!