In the development of reciprocating engines, the objectives have included the simultaneous improvement of the power, fuel and lubricant economy, and engine durability. To achieve these objectives, many tribological problems have had to be solved with regard to pistons, piston rings and cylinders, which are particularly crucial and complicated. Some of these problems are reviewed, and their main points of concern are listed as follows: (1) temperatures of the piston and the cylinder and their influences, including methods to keep them below critical values, (2) relations between the piston-ring motion, blow-by gas and oil consumption, (3) piston friction loss and its characteristics, (4) effects of multi-grade oil and friction modifiers on friction of the piston and cam, and (5) capability of the two-ring package to reduce piston friction, piston weight and engine height.