Using a recently developed instrument, the ELAS (English Language Anxiety Scale) based on the Foreign Language Classroom Anxiety Scale, this study examines English language anxiety in Mexican middle school girls. Of 178 middle school students (91 boys and 87 girls), it was shown that while there is no gender difference in ESL classes, girls are significantly more anxious about using English in their mainstream classes. This difference is partially explained by the different types of English language anxiety that manifest in ESL and mainstream classes. Various statistical procedures including ANCOVA and factor analysis support the conclusion that as ESL students move from ESL to mainstream classes their English language anxieties shift from academic types of worry to peer interactional concerns in which female students seem to feel more stress. Recommendations for teachers include the use of affective assessments, such as the ELAS, prior to complete mainstreaming and the development of safer group activities in which girls feel more comfortable.