Abstract: A two-stroke internal combustion engine having at least two cylinders which are aligned, each cylinder having a piston. The pistons are rigidly attached to each other by means of a piston rod which is provided with a carrier and exhaust valves, the valves being slidably arranged on the piston rod, and exhaust ducts which are provided for each cylinder at the ends facing each other. The facing ends also having valve seats. Intake ports having pressure controlled check valves are provided in each cylinder at the distal ends, and each combustion chamber is on the side of the piston which faces the other piston. The exhaust ducts are arranged in a guide for the common piston rod.