A piston for an internal combustion engine includes a piston crown (2) and a cylindrical side wall (4), an annular piston ring groove (8) being formed in the side wall (4) which accommodates an annular spring (14). The spring (14) includes an annular radially extending portion (16) and first (20) and second (22) projections. The radially extending portion (16) divides the annular groove into two chambers in the axial direction of the piston. The upper chamber closest to the piston crown accommodates an annular compression ring (10). The lower chamber furthest from the piston crown accommodates an annular oil scraper ring (12). The first projection (20) is arranged to contact the upper surface closest to the piston crown of the annular groove (8). The second projection (22) is arranged to contact the inner surface of the oil scraper ring (12) to urge it outwardly. The height of the upper chamber in the axial direction is greater than that of the compression ring (10), whereby in use, the pressure acting on the piston crown will act also on the inner surface of the compression ring (10) and urge it in the outward direction.