This research is an attempt to define effective teaching of mathematics as well as encourage effective teaching of mathematics. From reviewing the literature, this research proposed that teaching mathematics effectively involved deliberate communication with students to both demystify the content and to build self-efficacy. The purpose of this research was to determine if math teachers perceived their contacts with secondary math students to be more successful if they developed Effective Interaction Skills When Teaching Mathematics. This grouping included three skill sets: language practices, responding to student thinking, and affirmation and feedback. Within the skill sets there were 10 practical teaching skills: revoicing, expanding, compressing, stepping out, responding to student utterances, students evaluating students, addressing prior knowledge, descriptive feedback, encouragement and support, and addressing past and present feelings. Participating teachers attended professional development sessions, taught reflectively as they implemented the skills, and gave their impressions of the Effective Interaction Skills When Teaching Mathematics.