Focusing on teachers, research has revealed that teacher effectiveness in teaching is in part related to personality traits in teachers. According to the advocates of this aspect of language teaching, personality traits represent each person's biological and psychological characteristics that either foster or inhibit success in teaching and learning. In this study, the personality dimension of Introversion-Extroversion was examined in its relation to student talk in terms of turn-taking, the number of students who participated, and direction of talk--teacher-student or student-student--in speaking classes. Two hypotheses--that there is a relationship between the personality traits of introversion-extroversion in teachers and student talk, and that student participation would be higher in the classes of female teachers--were tested. The study was carried out with eight teachers-- two extroverted and two introverted males, and two extroverted and two introverted females. They were identified as introverts and extroverts based on the result of the Maudsley Personality Inventory (Eysenck, 1970). After this, each teacher's class was observed twice using the verbal flow chart (Richards and Nunan, 1990) to identify student talk in terms of turn-taking, the number of students who participated, and direction of talk. The data collected were analyzed with percentages and Chi-Square Tests. In addition, for post hoc analyses students' gender and type of teacher questions were also coded and compared with percentages. The results of the first hypothesis revealed that there is a significant difference (p<.001) between the classes of introverted and extroverted teachers in terms of turn-taking. In terms of the number of students who participated, a higher percentage of students (71.5%) participated in the classes of extroverted teachers than those of introverted teachers (64%). As for direction of talk, introverted teachers were found to have a higher ratio of teacher-student interactions (94% versus 74%), and extroverted teachers were found to have a higher ratio of student-student interactions (26% versus 6%). This indicates that students in classes of extroverted teachers had more opportunity to interact with each other. The results of the second hypothesis that student participation would be higher in the classes of female teachers revealed that in terms of turn-taking, the difference between extroverted males and females is not significant, while the difference between introverted male and female teachers is significant at the p<.005 level. As for the participation in terms of the number of students who participated, the highest participation was observed in the classes of extroverted female teachers (79%), and the lowest in the classes of introverted female teachers (54%). A comparison of student participation in the classes of male and female teachers as a whole indicated that student participation is higher in the classes of male teachers than female teachers (72.5% versus 66.5%). The results related to gender were contrary to what was hypothesized; that is, student participation was found to be higher in the classes of male teachers. Post hoc analysis of the data revealed that in the classes of male teachers, female student participation was higher than male student participation (81% versus 67%), and male student participation was higher than the female student participation (71% versus 56%)in the classes of female teachers. The second observation was that introverted teachers tended to ask more short-answer type questions, and extroverted teachers tended to ask more discussion type questions. In this study, the findings are expected to attract the attention of EFL teachers and curriculum designers in Turkey.