Summary: This study explored the themes that comprise preservice teachers’ attitudes regarding discourse in the K-12 mathematics classroom. The initial development of the theory underlying preservice teachers’ attitudes regarding mathematical discourse is documented through the development of a 5-point Likert instrument. Analysis of the Preservice Teachers’ Attitudes About Discourse in the Mathematics Classroom (PADM) Instrument (N = 277) resulted in three reliable factors: Promoting Mathematical Reasoning $α_1=0.85$, Examining Complex Mathematical Concepts $α_2=0.81$ and Valuing Students’ Mathematical Ideas $α_3=0.85$. These results suggest a framework that mathematics educators can employ to address preservice teachers’ attitudes regarding discourse in an effort to support their implementation of reform-based discourse in the teaching of mathematics in their future classrooms. (Contains 7 tables.) (ERIC)