['Group learning is the core of problem-based learning (PBL) but has not been extensively studied, especially in Asian students.', "This study compared students of PBL and non-PBL curricula in students' talking time and participation in small-group tutorials in a medical school in Asia. The proportions of student talking of 46 tutorials in three teaching rotations of the PBL curriculum and those of 43 corresponding tutorials in the non-PBL curriculum were counted. Twelve videotapes of tutorials (six from each curriculum), stratified for tutor, case scenario and students' learning stage, were randomly selected and transcribed. They were rated with the group-interaction (5 items) and active-participation (four items) tutorial assessment scales developed by Valle et al. These outcomes were compared between the students of PBL and non-PBL curricula.", 'Students from the PBL curriculum talked significantly more. In only two (4.7%) of 43 tutorials in the non-PBL curriculum did the students talk more than the tutors; but students talked more than the tutors in 17 (37.0%) of 46 tutorials in the PBL curriculum. PBL students scored significantly higher than non-PBL students in all items except one item (respect to peers) of the tutorial assessment scales, and in the mean scores of both the group interaction scale (items 1-5) and the active participation scale (items 6-9).'] Does pBL curriculum improve medical students ' participation in small-group tutorials?