Abstract: Fixing device for fixing two vertebra parts with respect too one another, and the method for fixing two vertebra parts. The fixing device comprises fixing plates which have to be secured to the relevant vertebra parts. The fixing plates are provided with countersunk openings for receiving the heads of fixing screws. Sleeves which project out of the fixing plates and are to be held in the vertebra adjoin these fixing openings. The fixing plates are fixed with respect to one another with the aid of a connecting system comprising two lips, which lie at a distance from one another, in one fixing plate and a tongue, which can be placed between the said lips, belonging to the other fixing plate. A clamping action of the tongue between the lips can be brought about by a spreading action.