In a two-stroke internal combustion engine, total hydrocarbon (THC) exhaust is decreased as a result of small structural changes and without loss of output power. A Schnurle scavenging-type combustion chamber has a hemispherical main surface and an annular skirt-like squish band, and a spark plug is disposed for a spark point to be substantially at the center of the combustion chamber. The squish band has minimized width.