The invention relates to a rotor for laboratory centrifuges which is designed for accommodating at least one centrifugation container, and an adapter for accommodating a sample vessel and for use in a laboratory centrifuge rotor. The rotor has at least one hold-down element by which the at least one centrifugation container is held in the rotor and protected from axial displacement. In addition, a contact pressure may be produced on the at least one centrifugation container on the rotor.