This study focuses on the influence of high school students' (10th and 11th grade) epistemological understanding and topic interest on their interpretation of a dual-position expository text about genetically modified food, as well as on the change in their beliefs about the topic. After reading, students were given different tasks: (1) to write a conclusion for the text, which presented two opposing positions but lacked an overall concluding paragraph, (2) to write personal comments on the text, (3) to answer questions on conceptual understanding, and (4) to rate their interest in the text. Participants were also asked to rate their beliefs about transgenic food before and after reading the text. The findings show the effects of students' level of epistemological understanding when writing conclusions to the text, and commenting on (a) the role of science and scientists' work with respect to nature, (b) the need for further scientific investigation, and (c) the effective value of transgenic food production. Students' topic interest affected their answers to the questions on the text arguments and their text-based interest. In addition, after reading, a change emerged in students' beliefs about the topic in relation to their epistemological understanding.