Problem-based learning (PBL) with simulated cases is one method of delivering standardized pediatric curricular objectives, but the fact that students are dispersed and participating in community-based practices makes group meetings difficult. To address these issues, researchers developed and tested a new modality for presenting PBL cases, a CD-ROM/Web hybrid computer program to standardize the national pediatric curriculum: Project Learning through Interactive Video Education (L.I.V.E.). Project L.I.V.E. used digital video case simulations to present PBL with the stimulus case followed by asynchronous case discussions among students at multiple clinical sites. The study sought to determine if critical thinking as shown by discourse among students during group discussion differed by presentation format. Approximately 128 medical students participated in 3 conditions: (1) a face-to-face group with text/paper case modality; (2) a face-to-face group with a video case modality; and (3) a virtual group with digital video case modality. Study findings suggest that the virtual group engaged in more critical thinking, as represented by their dialogue within the group, than did the other two modalities, perhaps because of the increased individual accountability required by the online discussion. However, the virtual group did have a reduced sense of group process. The findings also provide insight into the advantages of using video. (Contains 21 tables and 32 references.) (SLD)