Previous qualitative research on educational practices designed to improve critical thinking has relied on anecdotal or student self-reports of gains in critical thinking. Unfortunately, student self-report data have been found to be unreliable proxies for measuring critical thinking gains. Therefore, in the current interpretivist study, five educators whose students had demonstrated significant gains on a validated performance measure of critical thinking (CAT), were interviewed to understand what led to the exhibited gains in critical thinking. Participants' instruction and assessment methods were examined in order to better understand what practice led to student gains in critical thinking in their courses. Data were analyzed using inductive methods. Findings associated with instruction methods revealed that elements of problem-based learning (PBL), team-based learning (TBL), and individual readiness tasks (IRT) were present among all participant courses. With regards to assessment, participants used high-stakes assessments, low-stakes assessments, and informal evaluations of student development to assess student progress in their courses. While there were variations in approaches to assessment among educators, the assessments that were described emphasized some of the critical thinking skills associated with the CAT. Additionally, each educator's approach to instruction and assessment was strongly influenced by their own prior educational experiences. [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/en-US/products/dissertations/individuals.shtml.]