Prompted by research showing that communication is one element that distinguishes teachers rated effective by students from those rated ineffective, a study was undertaken to develop a scale for assessing the perceived communication effectiveness of graduate teaching assistants (GTAs). Two groups, one of undergraduate students and one of their graduate teaching assistants, identified the communication behaviors used in assessing the communication effectiveness of teachers. These findings were then used to create a scale that was administered to approximately 1,000 undergraduates in 60 classes taught by GTAs. The findings suggested that students perceived as effective those teachers who possessed organizational stability, instructional adaptability, and interpersonal flexibility. (Author/FL)