Abstract: The invention relates to an apparatus and a method for testing concrete/cement mixtures intended for use with cementing of casings in subsea bore holes for oil and/or gas wells. The apparatus comprises a chamber (1, 1') for the accommodation of a pipe-like test container (6) for the concrete sample. The chamber (1, 1') and, consequently, the pipe-like test container (6) as well as the concrete sample may be subjected to pressure and temperature conditions substantially simulating the conditions at the intentional place of application for the cement mixture, measuring instrument means being arranged for the measurement of i.e. temperature, hydrostatic pressure and differential pressure during that part of the test which is conducted within the chamber (1, 1').