First year allopathic (MD) and osteopathic (DO) students take histology as part of a 22 week combined cell biology and physiology course. The histology lab is based entirely on virtual slides: digitized slides that allow students to move the field of view and change magnification as with a microscope (BacusLabs).  Slides are viewed on large (21”) computer monitors shared by groups of 3 students. Students can work in independent groups, and monitors can also be linked to the view of the instructor, or to the view of any individual group. This is the first year that we have had the full capability of this system, and we are now applying the technology to well-researched ideas of small group learning in order to improve student understanding of histological principles. Each lab session revolves around a set of lab objectives and problems. Problems are assigned to individual groups, and a randomly selected member of the group explains the group’s answer to the rest of the class.  Student resistance is appreciable. Student surveys taken early and at the end of the course reveal their discomfort with both presenting answers and with listening to answers provided by other students, and their strong preference for the more familiar models of instructor didactic presentation and banks of sample exam questions.  At the same time, by the end of the course students appeared to be more comfortable with asking questions and expressing opinions in class. Furthermore, the practice of working in small groups of 3 or 4 was readily accepted throughout the duration of the course. The current laboratory format has also resulted in much higher attendance throughout the course (attendance is not required), than we have had in previous years with labs based on digitized slides or on glass slides. We plan to continue pursuing the problem based model, working to overcome the student resistance, refining the problems themselves, and developing rubrics for evaluating student learning.