This paper explores high school students' and teachers' preferences towards constructivist Internet-based learning environments. The study proposes a framework, including two dimensions and five aspects, to illustrate the features of the Internet-based learning environments. Based upon this framework, the "Constructivist Internet-based learning environment survey improvement" (CILESI) was developed, which includes the scales of ease of use, multiple sources, student negotiation, reflective thinking, critical judgement and epistemological awareness. Questionnaire responses gathered from 630 high school students in Taiwan suggested that the CILESI showed adequate reliability in assessing students' preferences. Male students placed more emphasis on the student negotiation, critical judgement and epistemological awareness enhanced by the Internet-based learning environments than female students did. In addition, the teachers of the sampled students (n=78) were also surveyed by CILESI. The teachers tended to express stronger preferences on the ease of use of the Internet-based learning environments than did their students. However, students, when compared with their teachers, seemed to express more preferences towards the features of student negotiation, reflective thinking, critical judgement and epistemological awareness of Internet-based learning environments.