The assessment of people's knowledge on biofuels is sporadic mainly due to a lack of an objective knowledge scale. We conducted large-scale mail surveys to fill the gap and assess people's knowledge of biofuels and the social-demographic characteristics related to this. We sent out mail surveys to 4733 valid addresses and received 1376 completed surveys. Biofuels knowledge was assessed with five items related to energy content, production capacity, and potential benefits and harm of biofuels, assigning + 1 or + 2 points for correct, and - 1 or - 2 points for incorrect answers depending upon respondents' certainty about the answer, and 0 point for 'I don't know' responses. We constructed a summary index by summing the points scored on the five items. The mean score for the biofuels knowledge index was 2.25 +/- 3.33 on the scale of - 10 to + 10 points. The multiple regression results showed that socio-demographic attributes are significant predictors of biofuels knowledge: men scored 1.65 points higher than women; for one level increment in education, respondents scored 0.26 points higher; and Democrats scored 1.34 points lower than others. Possible reasons for these results and their implications for policy and management to make cellulosic biofuels successful are discussed.