Little research has investigated how problem-based learning (PBL) instruction influences students' critical thinking and evidence-based practice. This research sought to ascertain if PBL instructional practices facilitated critical thinking and EBP; identify those practices; and, identify changes students made in tutorials.

A qualitative, two-case, critical case study design used pretest and posttests of the California Critical Thinking Skills Test (CCTST) (Facione, 1990) and Self-Evaluation of EBP adapted from Straus et al. (2005) to select the critical case sample. Students who made the greatest gains from pre to posttest scores met selection criteria for the critical case sample and were invited to participate in a one-to-one interview with the researcher. The interview focused on obtaining students' perceptions as to what group, PBL tutorial, and tutor factors they thought contributed to the change in their scores.

Thirty first year, second semester students and PBL tutors from the graduate occupational and physical therapy programs at one university participated. Triangulation of data increased credibility of the findings. Data included a total of eighteen ethnographic observations of six PBL tutorial groups on three occasions throughout the semester; interviews with ten students meeting selection criteria for the critical case sample; analysis of curriculum and course documents, and students' handouts they produced for PBL tutorials.

The study found that students made improvements in their critical thinking and EBP. The study exposed essential tutorial group elements that were instrumental in facilitating the development of students' critical thinking and EBP; group format, the tutor's facilitation skills, student's disposition; feedback, and the PBL method. Curriculum design emerged as critical in contributing to the development and application of EBP in PBL tutorials.

The study's findings revealed a need for ongoing tutor education and supervision and for specific pedagogical practices to be integrated across the curriculum to facilitate critical thinking and EBP. Students improved their critical thinking and EBP, with group format, tutors' modeling of critical thinking, student disposition, feedback, and curriculum design emerging as primarily influential. Implications for curriculum design, faculty education, and future research are discussed.