For the calculation of the stability of flat-oval pipes, equations were derived in former papers which proceeded from the Load carrying ability of the material to the fully plastic state of stresses. With strain controls on a pilot model under inside excess pressure, the permissiveness of the suppositions made and the validity of the equations derived were to be proven. The comparison of the stresses on the outside of the pipe surface and the highest inside excess pressure shows a good agreement between the values measured and the calculated ones, and confirms that the application of the newly developed formalism leads to a safe Lay-out of the stressed pipes.