Bioethanol (BE) can contribute to the reduction of greenhouse gases emissions. Korea will introduce a BE mandate of 5% BE and 95% gasoline (E5) until 2020. We assess the public’s willingness to pay (WTP) a premium for the introduction. The mean additional WTP for E5 is estimated to be KRW 290 (USD 0.26) per liter. This value amounts to 15.6% of the gasoline retail price (KRW 1856 or USD 1.70).