Summary: English proficiency influenced student questioning in terms of the types, frequency, domain, and target audience. Moreover, proficiency influenced teachers' questioning practices as well. Other factors, such as students' relative oral proficiency within the class, attitudes toward speaking in class, perceptions of classroom climate, previous language learning experience, environmental and motivational factors, and assumptions about how to speak a language, contributed to the complexity and differences in students' question asking and/or answering patterns. Teacher and student questioning in tandem contributed to students' on-line second language acquisition. Additional research needs to investigate whether classroom questioning has a lasting effect on second language acquisition.