The purpose of this study was to analyze Verbal Interaction in the classroom and Mathematics Achievement. The subjects of this study, selected from schools with 32 mathematical teachers, were 719 Prathom Suksa Seven students of Department of Education in Bangkok. They were randomly selected to represent the mathematics field. Two Research instruments used in collecting the data. The Flanders’ Interaction Analysis Technique was in categorizing teacher-student verbal interaction in the classroom. The Mathematics Achievement Test was administered to the students. The data were analyzed using such statistics as I/D Ratio, T/S Ratio, mean, and F-test for the Groups-Within-Treatments. The Hypotheses were tested at the .05 level of significance. The findings indicated that there were no significant differences at the .05 level between Indirect Teacher and Direct Teacher interaction involved with mathematics achievement. There were no significant differences at the .05 level between Teacher Talk and student Talk involved with mathematics achievement. The range of I/D Ratio was 0.37 to 2.14, and the range of T/S Ratio was 1.10 to 3.90.