Heat transfer from a piston must be large on the lower part of the liner below the bottom dead centre of the piston, since the temperature difference increases towards the lower part and moreover the piston speed becomes very low. From the view point of piston cooling, it will be more effective to cool sufficiently the lower part of the liner. To verify this expectation, experiments were carried out on a two-cycle engine, in which the temperatures of the piston and the liner were measured, chainging the cooling method of the liner. By comparing the heat transfer coefficients and the heat distributions, the following facts were found. (1) Heat transferred from the piston to the liner is largest near the top ring, when the piston is at the bottom dead centre. (2) In the case of poor cooling of the lower part of the liner, the piston temperature becomes high, especially at the piston skirt. (3) In the case of sufficient cooling of the lower part of the liner, the heat load of the top ring is partly distributed to the lower rings.