Results from this study show that the use of online discussion forums as an instructional tool in a face-to-face course improved undergraduate preservice teachers' critical thinking skills. Participants in the study were 93 students registered in four sections of an Educational Psychology course at a Midwestern university. To control for learning preferences, all participants in the study took the Canfield Learning Style Inventory as a pre-test. Students also completed the Ennis-Weir Test of Critical Thinking as pre- and post-tests. In two of the four sections students used the Blackboard virtual learning environment to complete weekly discussions on course topics as part of their regular coursework. Quantitative analysis results from the critical thinking measure showed an increase in students' critical thinking skills over the course of the semester. The analysis of online postings demonstrates an increase in higher order thinking skills as measured with a rubric based on Bloom's taxonomy. Quantitative and qualitative analyses are presented along with implications for teaching and learning. (Contains 4 tables.)