The stretchable semitrailer or chassis is hitched to a truck tractor for transporting containers. It comprises an elongate frame structure including a front frame section, and a rear frame section provided with a set of wheels. The rear frame section is mounted to slide longitudinally on the front frame section between an extended position and a retracted position. The frame structure can receive and support, in the extended position of the rear frame section, a series of two containers of given length, or one container having twice this given length. The front frame section comprises, in the retracted position of the rear frame section, a rear loading area for receiving and supporting a container having the above mentioned given length, with the set of wheels positioned under that container. The rear frame section comprises at the rear thereof a fifth wheel for hitching to the rear frame section a second chassis for transporting at least one additional container.