This study investigated whether role assignment and proficiency difference in pair work affect low level learners’ production and task performance in English. A total of 16 Korean EFL high school students, in dyads of same or different proficiency levels, performed two information gap tasks, one in free interaction and one with role assignment. Their pair interaction was analyzed according to task completion,words, C-units, and interactional modifications. The results showed overall that assigning a dominant role to learners resulted in an increase in their production of words and C-units as well as task completion. The increase was particularly strong among learners who showed passive participation in free interaction. While the influence of role assignment did not differ greatly in homogeneous and heterogeneous pairings, low homogeneous pairs exhibited difficulty in performing tasks. These results suggest that it is possible to facilitate low level learners’ pair interaction by assigning leading roles and pairing them with higher level learners.