The effect of the inter-ring crevice, the volume between the top and the second piston rings, on unburned hydrocarbon(UHC) emission was experimentally investigated. The ultimate goal of this study is to reduce the level of UHC emission by minimizing the effect of the inter-ring crevice. For this purpose the unburned mixture trapped in the inter-ring crevice was extracted to the crankcase during the late period of the expansion stroke and the early period of the exhaust stroke through the engraved grooves on the lower part of the cylinder wall. The extraction of the mixture resulted in significant reductions of UHC emission over a range of speeds and loads, without any losses of efficiency and power. The effect of the inter-ring crevice on UHC emission in an SI engine was obvious.