This paper contemplates how corpus evidence might be used to address teachers' questions about English grammar and suggests that corpus linguistics has an important role to play in raising their awareness to linguistic features and patterns. The article surveys a range of grammatical questions posted by EFL/ESL teachers on four Orkut communities devoted to the teaching and learning of English. It concentrates on three specific types of questions: synonymous lexical items which function differently and are reported to be difficult to teach and explain; linguistic evidence that contradicts the prescriptive grammar rules that teachers have been taught during their education; and collocations that teachers attempt to explicate. In attempting to address the teachers' questions, corpus evidence is used to offer possible explanations. It is suggested that the use of corpus data in addressing these questions is not only convincing but also leads to discoveries of patterns and meanings which might not be found in other reference materials such as grammars and dictionaries