The purpose of this study was to explore and discover classroom management problems encountered by undergraduate science teaching assistants (TAs). Information about TA perceptions of classroom management problems was obtained to better understand how gender, teaching experience, and academic discipline affected their classroom management experiences. Study subjects consisted of 25 TAs in various science departments (e.g. physics, chemistry, and biology) at a large Midwestern University. Sixty percent (n=15) of them were male, and forty percent (n=10) were female. Regarding subjects' teaching experience with undergraduate level students, twenty percent (n=5) of them possessed three years or more teaching experience, forty percent (n=10) had teaching experience between one and three years, and the other forty percent (n=10) had a teaching experience of one year at the time of the study. An Email survey was used for data collection from 125 graduate TAs in various science departments. TAs' responded to ten challenging student behaviors in the classroom that were developed from DiGiulio's (1995) questionnaire. Results from this study reveal a variance in classroom management problems were primarily due to TA type (United States Teaching Assistants or International Teaching Assistants). (Contains 2 tables.)