We investigated the feasibility of using an audience response system (ARS) to measure and immediately display the effect of lectures on food safety, related to pesticide residue and radiological substances, on an audience’s responses. Students were asked closed questions about typical misperceptions related to food safety, both during and after their lectures. In Experiment 1, 105 students answered six true-or-false questions, including those about pesticide residue and bovine spongiform encephalopathy (BSE). In Experiment 2, 101 students also answered six true-or-false questions, but one question about BSE was replaced by a question about radioactive material. All students responded using an ARS, and the overall true/false rate for each question was displayed to them immediately after each response. The results reveal that the proportion of questions answered correctly was higher after the lecture than during the lecture in both experiments. In addition, the number of participants who answered each question correctly after the lecture was significantly larger than that during the lecture for four of the six questions in both experiments. This study indicates that the effect of a food safety lecture on students’ understanding is easily measurable using an audience response system.