Computer mediated communication (CMC) offers new opportunities for learners to create communities of inquiry that allow for more active learning. This paper reports on the use of a Learning Management System (LMS) as a tool to facilitate students' writing and critical thinking skills. The primary data for the study came from students' online learning records and from discussion forum postings in the LMS. It was found that students' motivation to learn was at a high level. Most importantly, student motivation was positively correlated with their learning behavior. Although male and female students did not differ in their motivation and learning behavior, messages in the writing forum indicated that female students had higher critical thinking skills than male students. "Explaining" messages appeared the most often, while "interpreting" messages appeared the least. The process of text-based online discussion in the forum had the potential to enhance the students' writing skills, encourage their critical thinking, and help them write more systematically. The practical implications of these findings are discussed.