This study examined the influence of instructor-facilitated Socratic questioning in online discussions on the critical thinking skills of undergraduate students enrolled in a proprietary institution with nonselective admissions criteria. A sample of students was purposively selected from two sections of an online introductory business course, with the expectation that these students would have diverse critical thinking skills. Two questions guided the study. How does instructor-facilitated Socratic questioning influence students' critical thinking in online discussions? Do students who receive instructor-facilitated Socratic questioning in online discussions participate more frequently in discussions than those who do not receive Socratic questioning? To address these questions, 25 participants were randomly assigned to two groups-a treatment group that received Socratic questioning in response to discussion messages or a control group that received traditional responses. Six discussions were analyzed using two methods of content analysis. Additionally, a pretest and a posttest of the California Critical Thinking Skills Test were administered. Qualitative and quantitative analysis using descriptive statistics, independent "t"-tests, chi-square tests, and a Wilcoxon test were used to analyze the data. The findings of the study revealed that Socratic questioning, compared with traditional instructional methods, did not have a statistically significant influence on the critical thinking of students with diverse critical thinking skills. Frequency of participation also was not affected by Socratic questioning. These findings are contrary to studies in which students with initially higher critical thinking skills increased their levels of critical thinking and participation in discussions as a result of Socratic questioning. The findings are supported, however, by other research indicating that low critical thinkers may not benefit from high problem solving instructional methods (Williams, Oliver, Allin, Winn, & Booher, 2003). [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]